COVID-19 vaccine reactogenicity among participants enrolled in the GENCOV study

BACKGROUND

GENCOV is a prospective, observational cohort study of COVID-19-positive adults. Here, we characterize and compare side effects between COVID-19 vaccines and determine whether reactogenicity is exacerbated by prior SARS-CoV-2 infection.

METHODS

Participants were recruited across Ontario, Canada. Participant-reported demographic and COVID-19 vaccination data were collected using a questionnaire. Multivariable logistic regression was performed to assess whether vaccine manufacturer, type, and previous SARS-CoV-2 infection are associated with reactogenicity.

RESULTS

Responses were obtained from n = 554 participants. Tiredness and localized side effects were the most common reactions across vaccine doses. For most participants, side effects occurred and subsided within 1-2 days. Recipients of Moderna mRNA and AstraZeneca vector vaccines reported reactions more frequently compared to recipients of a Pfizer-BioNTech mRNA vaccine. Previous SARS-CoV-2 infection was independently associated with developing side effects.

CONCLUSIONS

We provide evidence of relatively mild and short-lived reactions reported by participants who have received approved COVID-19 vaccines.

COVID-19 vaccine safety surveillance systems

The U.S. COVID-19 vaccination program, which commenced in December 2020, has been instrumental in preventing morbidity and mortality from COVID-19 disease. Safety monitoring has been an essential component of the program. The federal government undertook a comprehensive and coordinated approach to implement complementary safety monitoring systems and to communicate findings in a timely and transparent way to healthcare providers, policymakers, and the public. Monitoring involved both well-established and newly developed systems that relied on both spontaneous (passive) and active surveillance methods. Clinical consultation for individual cases of adverse events following vaccination was performed, and monitoring of special populations, such as pregnant persons, was conducted. This report describes the U.S. government's COVID-19 vaccine safety monitoring systems and programs used by the Centers for Disease Control and Prevention, the U.S. Food and Drug Administration, the Department of Defense, the Department of Veterans Affairs, and the Indian Health Service. Using the adverse event of myocarditis following mRNA COVID-19 vaccination as a model, we demonstrate how the multiple, complementary monitoring systems worked to rapidly detect, assess, and verify a vaccine safety signal. In addition, longer-term follow-up was conducted to evaluate the recovery status of myocarditis cases following vaccination. Finally, the process for timely and transparent communication and dissemination of COVID-19 vaccine safety data is described, highlighting the responsiveness and robustness of the U.S. vaccine safety monitoring infrastructure during the national COVID-19 vaccination program.

Safety monitoring of bivalent mRNA COVID-19 vaccine among pregnant persons in the vaccine adverse event reporting System - United States, September 1, 2022 - March 31, 2023

BACKGROUND

Pregnant persons are at increased risk of severe COVID-19 illness. Bivalent mRNA COVID-19 vaccination is recommended for everyone, including pregnant persons. However, data are limited on the safety of bivalent mRNA COVID-19 vaccination during pregnancy.

OBJECTIVE

To evaluate and summarize reports to the Vaccine Adverse Event Reporting System (VAERS), a national spontaneous reporting system, among pregnant persons who received bivalent mRNA COVID-19 vaccine.

METHODS

VAERS U.S. reports of adverse events (AEs) in pregnant persons who received the bivalent mRNA COVID-19 vaccine from 9/1/2022-03/31/2023 were identified. Clinicians reviewed all reports and available medical records. AEs of these reports were compared with AEs reported to VAERS following monovalent mRNA COVID-19 booster vaccination in pregnancy.

RESULTS

VAERS received 136 reports for pregnant persons who received bivalent mRNA COVID-19 vaccine; 87 (64 %) after BNT162b2 (Pfizer-BioNTech), and 48 (35 %) after mRNA-1273 (Moderna); 28 (20.6 %) reports were classified as serious. The most common pregnancy-specific outcomes reported included 12 (8.8 %) spontaneous abortions (<20 weeks gestation), 6 (4.4 %) episodes of preterm delivery, and 5 (3.7 %) reports of preeclampsia. One stillbirth (≥20 weeks gestation) was reported. No maternal or infant deaths were reported. There were 6 reports of AEs in infants, which included 3 reports of admissions to the neonatal intensive care unit: two infants with low birth weight, and one infant with a patent ductus arteriosus and patent foramen ovale. Non-pregnancy-specific adverse events were mostly COVID-19 infection and systemic reactions (e.g., headache, fatigue). Pregnancy-specific conditions were reported less frequently after bivalent mRNA COVID-19 vaccination compared to monovalent mRNA COVID-19 booster vaccination (3rd and 4th dose).

CONCLUSIONS

Based on this review of reports to VAERS, the safety profile of bivalent mRNA COVID-19 vaccination in pregnant persons was comparable to that observed for monovalent mRNA COVID-19 booster vaccination (3rd and 4th dose) in pregnant persons.

Effectiveness and safety of COVID-19 vaccination in people with blood cancer

BACKGROUND

People with blood cancer have increased risk of severe COVID-19 outcomes and poor response to vaccination. We assessed the safety and effectiveness of COVID-19 vaccines in this vulnerable group compared to the general population.

METHODS

Individuals aged ≥12 years as of 1st December 2020 in the QResearch primary care database were included. We assessed adjusted COVID-19 vaccine effectiveness (aVE) against COVID-19-related hospitalisation and death in people with blood cancer using a nested matched case-control study. Using the self-controlled case series methodology, we compared the risk of 56 pre-specified adverse events within 1-28 days of a first, second or third COVID-19 vaccine dose in people with and without blood cancer.

FINDINGS

The cohort comprised 12,274,948 individuals, of whom 81,793 had blood cancer. COVID-19 vaccines were protective against COVID-19-related hospitalisation and death in people with blood cancer, although they were less effective, particularly against COVID-19-related hospitalisation, compared to the general population. In the blood cancer population, aVE against COVID-19-related hospitalisation was 64% (95% confidence interval [CI] 48%-75%) 14-41 days after a third dose, compared to 80% (95% CI 78%-81%) in the general population. Against COVID-19-related mortality, aVE was >80% in people with blood cancer 14-41 days after a second or third dose. We found no significant difference in risk of adverse events 1-28 days after any vaccine dose between people with and without blood cancer.

INTERPRETATION

Our study provides robust evidence which supports the use of COVID-19 vaccinations for people with blood cancer.

Post-marketing surveillance of intussusception after Rotarix administration in Afghanistan, 2018-2022

BACKGROUND

In January 2018, Afghanistan introduced the monovalent oral rotavirus vaccine (Rotarix) nationwide, administered as a 2-dose series at six and ten weeks of age. We describe characteristics of intussusception cases and assess potential intussusception risk associated with Rotarix vaccination in Afghan infants.

METHODS

Multi-center prospective active hospital-based surveillance for intussusception was conducted from May 2018 to March 2022 in four sentinel sites in Afghanistan. We applied the Brighton Level 1 criteria for intussusception and verified vaccination status by reviewing vaccine cards. We used the self-controlled case series (SCCS) methodology to compare intussusception incidence in the 1 to 21 days after each dose of Rotarix vaccination against non-risk periods.

RESULTS

A total of 468 intussusception cases were identified in infants under 12 months, with 264 cases aged between 28 and 245 days having confirmed vaccination status contributing to the SCCS analysis. Most case-patients (98 %) required surgery for treatment, and over half (59 %) of those who underwent surgery required intestinal resection. Nineteen (7 %) case-patients died. Eighty-six percent of case-patients received the first dose of Rotarix, and 69 % received the second dose before intussusception symptom onset. There was no increased risk of intussusception in the 1-7 days (relative incidence: 0.9, 95 % CI: 0.1, 7.5), 8-21 days (1.3, 95 % CI: 0.4, 4.2), or 1-21 days (1.1, 95 % CI: 0.4, 3.4) following receipt of the first dose or in the 1-7 days (0.2, 95 % CI: 0.3, 1.8), 8-21 days (0.7, 95 % CI: 0.3, 1.5), or 1-21 days (0.6, 95 % CI: 0.3, 1.2) following the second dose.

CONCLUSION

Rotarix vaccination was not associated with an increased intussusception risk, supporting its continued use in Afghanistan's immunization program. However, there was a high level of death and resection due to intussusception among Afghan infants.

Prediction and detection of side effects severity following COVID-19 and influenza vaccinations: utilizing smartwatches and smartphones

Vaccines stand out as one of the most effective tools in our arsenal for reducing morbidity and mortality. Nonetheless, public hesitancy towards vaccination often stems from concerns about potential side effects, which can vary from person to person. As of now, there are no automated systems available to proactively warn against potential side effects or gauge their severity following vaccination. We have developed machine learning (ML) models designed to predict and detect the severity of post-vaccination side effects. Our study involved 2111 participants who had received at least one dose of either a COVID-19 or influenza vaccine. Each participant was equipped with a Garmin Vivosmart 4 smartwatch and was required to complete a daily self-reported questionnaire regarding local and systemic reactions through a dedicated mobile application. Our XGBoost models yielded an area under the receiver operating characteristic curve (AUROC) of 0.69 and 0.74 in predicting and detecting moderate to severe side effects, respectively. These predictions were primarily based on variables such as vaccine type (influenza vs. COVID-19), the individual's history of side effects from previous vaccines, and specific data collected from the smartwatches prior to vaccine administration, including resting heart rate, heart rate, and heart rate variability. In conclusion, our findings suggest that wearable devices can provide an objective and continuous method for predicting and monitoring moderate to severe vaccine side effects. This technology has the potential to improve clinical trials by automating the classification of vaccine severity.

Perinatal outcomes and sinopharm BBIBP-CorV vaccination during pregnancy

BACKGROUND

After the outbreak of COVID-19, a huge part of the health care services was dedicated to preventing and treating this disease. In case of COVID-19 infection, severe COVID-19 is reported more in pregnant individuals. Afterward, Vaccination against SARS-CoV-2 became a hot topic due to known effects in preventing severe COVID-19 during pregnancy. Vaccination of pregnant individuals started in August 2021 with the Sinopharm vaccine in Iran. The aim of current study was to determine the incidence of perinatal outcomes in women who were vaccinated during pregnancy.

METHOD

This retrospective cohort study included 129,488 singleton births from March 21, 2021, until March 21, 2022, in Tehran, Iran. The data was obtained from the Iranian Maternal and Neonatal (IMaN) Network and the Maternal Vaccination Registry. Adverse perinatal outcomes investigated in this study include preterm birth, extremely preterm birth, low birth weight, very low birth weight, intrauterine growth restriction, stillbirth, neonatal intensive care unit admission, congenital anomaly, neonatal death and low 5-minute Apgar score. The risk of all perinatal outcomes was evaluated using multiple logistic regression. The analysis was done using STATA version 14.

RESULTS

Of all 129,488 singleton births included in this study, 17,485 (13.5%) were vaccinated against SARS-CoV-2 (all with Sinopharm (BBIBP-CorV)). The exposure to the Sinopharm vaccine during pregnancy caused a significant decrease in the incidence of preterm birth (P =0.006, OR=0.91 [95% CI, 0.85 to 0.97]), extremely preterm birth (P =<0.001,OR=0.55 [95% CI, 0.45 to 0.66]), and stillbirth (P =<0.001, OR=0.60 [95% CI, 0.47 to 0.76]). Exposure to vaccination during the first trimester was associated with an increased risk of preterm birth (P =0.01, OR=1.27 [95% CI, 1.04 to 1.55]) Maternal vaccination during pregnancy was not associated with an increased risk of other adverse perinatal outcomes included in this study.

CONCLUSION

The finding of this population-based study indicated no adverse pregnancy outcome due to vaccination with the Sinopharm vaccine during the second and third trimesters of pregnancy. Overall risk of adverse pregnancy outcomes were lower in the vaccinated individuals compared to the unvaccinated group. Also, vaccination during the first trimester was associated with an increased risk of preterm birth.

CDC COVID-19 Vaccine Pregnancy Registry: Design, data collection, response rates, and cohort description

The U.S. Centers for Disease Control and Prevention (CDC) developed and implemented the CDC COVID-19 Vaccine Pregnancy Registry (C19VPR) to monitor vaccine safety. Potential participants who received a COVID-19 vaccine in pregnancy or up to 30 days prior to their pregnancy-associated last menstrual period were eligible to participate in the registry, which monitored health outcomes of participants and their infants through phone interviews and review of available medical records. Data for select outcomes, including birth defects, were reviewed by clinicians. In certain cases, medical records were used to confirm and add detail to participant-reported health conditions. This paper serves as a description of CDC C19VPR protocol. We describe the development and implementation for each data collection aspect of the registry (i.e., participant phone interviews, clinical review, and medical record abstraction), data management, and strengths and limitations. We also describe the demographics and vaccinations received among eligible and enrolled participants. There were 123,609 potential participants 18-54 years of age identified from January 2021 through mid-June 2021; 23,339 were eligible and enrolled into the registry. Among these, 85.3 % consented to medical record review for themselves and/or their infants. Participants were majority non-Hispanic White (79.1 %), residents of urban areas (93.3 %), and 48.3 % were between 30 and 34 years of age. Most participants completed the primary series of vaccination by the end of pregnancy (89.7 %). Many participants were healthcare personnel (44.8 %), possibly due to the phased roll-out of the vaccination program. The registry continues to provide important information about the safety of COVID-19 vaccination among pregnant people, a population with higher risk of poor outcomes from COVID-19 who were not included in pre-authorization clinical trials. Lessons learned from the registry may guide development and implementation of future vaccine safety monitoring efforts for pregnant people and their infants.

Safety of a second homologous Ad26.COV2.S vaccine among healthcare workers in the phase 3b implementation Sisonke study in South Africa

The Sisonke 2 study provided a homologous boost at least 6 months after administration of the priming dose of Ad26.COV2.S for healthcare workers enrolled on the Sisonke phase 3b implementation study. Safety monitoring was via five reporting sources: (i.) self-report through a web-link; (ii.) paper-based case report forms; (iii.) a toll-free telephonic reporting line; (iv.) healthcare professionals-initiated reports; and (v.) active linkage with National Disease Databases. A total of 2350 adverse events were reported by 2117 of the 240 888 (0.88%) participants enrolled; 1625 of the 2350 reported events are reactogenicity events and 28 adverse events met seriousness criteria. No cases of thrombosis with thrombocytopaenia syndrome were reported; all adverse events including thromboembolic disorders occurred at a rate below the expected population rates apart from one case of Guillain Barre Syndrome and one case of portal vein thrombosis. The Sisonke 2 study demonstrates that two doses of Ad26.COV2.S is safe and well tolerated; and provides a feasible model for national pharmacovigilance strategies for low- and middle-income settings.

Safety of incidental exposure to the novel oral poliovirus vaccine type 2 in pregnancy: A longitudinal observational study in Mozambique, 2022-2023

BACKGROUND

To minimize the risk of vaccine-derived poliovirus emergences, the novel oral poliovirus vaccine type 2 (nOPV2), was bioengineered to have increased genetic stability compared to Sabin OPV and recommended for outbreak response Emergency Use Listing by WHO. Although pregnant women are not a target population for this vaccine, a theoretical risk of incidental exposure exists via pharyngeal or faecal shedding from vaccinated children in the household or close community.

METHODS

This was an observational study of pregnant women conducted in Nampula (exposed cohort) and Maputo (non-exposed cohort) in Mozambique from August 2022 to June 2023. Two nOPV2 campaigns were conducted in Nampula and none in Maputo. Women were followed-up during routine prenatal consultation, delivery, and 28-day neonate visits for obstetric anomalies and pregnancy outcomes. Sociodemographic, medical, and obstetric history was captured.

RESULTS

Three hundred twenty-six pregnant women were enrolled from Nampula and 940 from Maputo City. Stillbirth prevalence (2·3% vs 1·6%, p = 0·438), low birth weight (8·9% vs 8·2%, p = 0·989), congenital anomalies (1 % vs 0·5%, p = 0·454), neonatal death (2·3% vs 1·6%, p = 0·08), and maternal death (0 % vs 0·2%, p = 0·978) did not differ amongst exposed and non-exposed cohorts. There was an increased rate of pre-term delivery in the exposed cohort (18·4% vs 11·0%, p = 0·011).

CONCLUSION

We did not observe an increased frequency of adverse pregnancy outcomes due to passive nOPV2 exposure. A higher frequency of preterm delivery needs to be further investigated. The data reported herein support the continued use of nOPV2 for poliovirus outbreak response and full licensure of the vaccine.

Humoral and cellular immunogenicity, effectiveness and safety of COVID-19 mRNA vaccination in patients with pediatric rheumatic diseases: A prospective cohort study

OBJECTIVES

To evaluate immunogenicity, effectiveness and safety of COVID-19 vaccination in patients with pediatric autoimmune inflammatory rheumatic disease (pedAIIRD).

METHODS

A prospective cohort study was performed at the pediatric rheumatology department of the Wilhelmina Children's Hospital in Utrecht, the Netherlands. Vaccination dates, COVID-19 cases and vaccine-related adverse events (AEs) were registered for all pedAIIRD patients during regular clinic visits from March 2021 - August 2022. SARS-CoV-2 IgG antibody levels and T-cell responses were measured from serum samples after vaccination, and clinical and drug therapy data were collected from electronic medical records. Rate of COVID-19 disease was compared between vaccinated and unvaccinated patients in a time-varying Cox regression analysis.

RESULTS

A total of 157 patients were included in this study and 88 % had juvenile idiopathic arthritis (JIA). One hundred thirty-seven patients were fully vaccinated, of which 47 % used biological agents at the time of vaccination, and 20 patients were unvaccinated. Geometric mean concentrations (GMCs) of post-vaccine antibody levels against SARS-CoV-2 were above the threshold for positivity in patients who did and did not use biological agents at the time of vaccination, although biological users demonstrated significantly lower antibody levels (adjusted GMC ratio: 0.38, 95 % CI: 0.21 - 0.70). T-cell responses were adequate in all but two patients (9 %). The adjusted rate of reported COVID-19 was significantly lower for fully vaccinated patients compared to non-vaccinated patients (HR: 0.53, 95 % CI: 0.29 - 0.97). JIA disease activity scores were not significantly different after vaccination, and no serious AEs were reported.

CONCLUSIONS

COVID-19 mRNA vaccines were immunogenic (both cellular and humoral), effective and safe in a large cohort of pedAIIRD patients despite their use of immunosuppressive medication.

What would have happened anyway? Population data source considerations when estimating background incident rates of adverse events following immunisation to inform vaccine safety

INTRODUCTION

Understanding background incident rates of adverse events following immunisation (AEFI) is essential to rapidly detect, evaluate, respond to, and communicate about vaccine safety concerns, especially for new vaccines. Creating estimates based on geographic specific population level data is increasingly important, as new AEFI presentations will be subject to the same local influences of population demography, exposures, health system variations and level of health care sought.

METHODS

We conducted a retrospective cohort analysis of hospital admissions, emergency department presentations and general practice consultations from 2015 to 2019-before introduction of COVID-19, Mpox or Shingrix vaccination-to estimate background incident rates for 37 conditions considered potential AEFI of special interest (AESI). Background incident rates per 100,000 population were calculated and presented as cases expected to occur coincidentally 1 day, 1 week and 6 weeks post-vaccination, by life-stage age-groups and presenting healthcare setting. We then assessed the proportional contribution of each data source to inform each AESI background rate estimate.

RESULTS

16,437,156 episodes of the 37 AESI were identified. Hospital admissions predominantly informed 19 (51%) of AESI, including exclusively ADEM and CVST; 8 AESI (22%) by primary care, and 10 (27%) a mix. Four AESI (allergic urticaria, Bell's palsy, erythema multiform and sudden death) were better informed by emergency presentations than admissions, but conversely 11 AESI (30%) were not captured in ICD-10 coded emergency presentations at all.

CONCLUSIONS

Emergent safety concerns are inevitable in population-wide implementation of new vaccines, therefore understanding local background rates aids both safety signal detection as well as maintaining public confidence in vaccination. Hospital and primary care data sources can be interrogated to inform expected background incident rates of adverse events that may occur following vaccination. However, it is necessary to understand which data-source provides best intelligence according to nature of condition and presenting healthcare setting.

COVID-19 Vaccine Safety Technical (VaST) Work Group: Enhancing vaccine safety monitoring during the pandemic

During the COVID-19 pandemic, candidate COVID-19 vaccines were being developed for potential use in the United States on an unprecedented, accelerated schedule. It was anticipated that once available, under U.S. Food and Drug Administration (FDA) Emergency Use Authorization (EUA) or FDA approval, COVID-19 vaccines would be broadly used and potentially administered to millions of individuals in a short period of time. Intensive monitoring in the post-EUA/licensure period would be necessary for timely detection and assessment of potential safety concerns. To address this, the Centers for Disease Control and Prevention (CDC) convened an Advisory Committee on Immunization Practices (ACIP) work group focused solely on COVID-19 vaccine safety, consisting of independent vaccine safety experts and representatives from federal agencies - the ACIP COVID-19 Vaccine Safety Technical Work Group (VaST). This report provides an overview of the organization and activities of VaST, summarizes data reviewed as part of the comprehensive effort to monitor vaccine safety during the COVID-19 pandemic, and highlights selected actions taken by CDC, ACIP, and FDA in response to accumulating post-authorization safety data. VaST convened regular meetings over the course of 29 months, from November 2020 through April 2023; through March 2023 FDA issued EUAs for six COVID-19 vaccines from four different manufacturers and subsequently licensed two of these COVID-19 vaccines. The independent vaccine safety experts collaborated with federal agencies to ensure timely assessment of vaccine safety data during this time. VaST worked closely with the ACIP COVID-19 Vaccines Work Group; that work group used safety data and VaST's assessments for benefit-risk assessments and guidance for COVID-19 vaccination policy. Safety topics reviewed by VaST included those identified in safety monitoring systems and other topics of scientific or public interest. VaST provided guidance to CDC's COVID-19 vaccine safety monitoring efforts, provided a forum for review of data from several U.S. government vaccine safety systems, and assured that a diverse group of scientists and clinicians, external to the federal government, promptly reviewed vaccine safety data. In the event of a future pandemic or other biological public health emergency, the VaST model could be used to strengthen vaccine safety monitoring, enhance public confidence, and increase transparency through incorporation of independent, non-government safety experts into the monitoring process, and through strong collaboration among federal and other partners.

Benefit-risk assessment of vaccines

Benefit-risk assessment (BRA) is critical for decision-making throughout the vaccine life cycle. It requires scientific assessment of evidence to make an informed judgment on whether the vaccine has a favourable benefit-risk profile i.e. the benefits of the vaccine outweigh its risks for use in its intended indication. The assessment must also consider data gaps and uncertainties, using sensitivity analyses to show the impact of these uncertainties in the assessment. The BRA field has advanced considerably over the past years, including the use of structured BRA frameworks, quantitative BRA models and use of the patient experience data. Analytical tools and procedures to standardize BRA implementation have become increasingly important. A Benefit-Risk Assessment Module has been prepared to enable the planning, assessment, and communication of relevant BRA information via a structured B-R framework. The module can help facilitate the conduct and communication of defensible BRAs by vaccine developers, funders, regulators and policy makers in high, middle or low-income countries, both for regulatory submissions and in public health responses to infectious diseases, including for epidemics.

The Brighton collaboration standardized module for vaccine benefit-risk assessment

Vaccine Benefit-Risk (B-R) assessment consists of evaluating the benefits and risks of a vaccine and making a judgment whether the expected key benefits outweigh the potential key risks associated with its expected use. B-R supports regulatory and public health decision-making throughout the vaccine's lifecycle. In August 2021, the Brighton Collaboration's Benefit-Risk Assessment of VAccines by TechnolOgy (BRAVATO) Benefit-Risk Assessment Module working group was established to develop a standard module to support the planning, conduct and evaluation of structured B-R assessments for vaccines from different platforms, based on data from clinical trials, post-marketing studies and real-world evidence. It enables sharing of relevant information via value trees, effects tables and graphical depictions of B-R trade-offs. It is intended to support vaccine developers, funders, regulators and policy makers in high-, middle- or low-income countries to help inform decision-making and facilitate transparent communication concerning development, licensure, deployment and other lifecycle decisions.

Immunogenicity and safety of a second heterologous booster dose of NVX-CoV2373 (TAK-019) in healthy Japanese adults who had previously received a primary series of COVID-19 mRNA vaccine: Interim analysis report of a phase 3 open-label trial

BACKGROUND

The phase 3, single-arm, open-label TAK-019-3001 study assessed two heterologous booster doses of NVX-CoV2373 administered 5 months apart in healthy Japanese adults who had completed a primary series of a COVID-19 mRNA vaccine 6-12 months previously. In the main part of this study, a first booster induced rapid and robust anti-SARS-CoV-2 immune responses, addressing waning immunity in participants.

METHODS

This interim analysis evaluated the immunogenicity and safety of a second booster in the extension part of this study including comparisons with the first booster. Immunogenicity was assessed on extension day (ED) 1 (before vaccination) and ED15. Solicited and unsolicited adverse events occurring in the 7 and 28 days, respectively, after vaccination were assessed.

RESULTS

Of the 150 participants who received a first NVX-CoV2373 booster, 129 were administered a second booster on ED1. Participant characteristics were consistent between the main and extension parts of the study. Titres of anti-SARS-CoV-2 rS serum immunoglobulin G and serum neutralizing antibodies against the SARS-CoV-2 ancestral strain at ED15 were 4.0- and 3.0-fold higher, respectively, than those observed 5 months after the first booster on ED1, and 3.0- and 1.4-fold higher, respectively, than those observed 14 days after the first booster on day 15. The proportions of participants who experienced solicited local and systemic adverse events (AEs) in the 7 days after the second booster were 73.6 % and 51.2 %, respectively: most were of grade 2 severity or lower. Seven percent of participants experienced unsolicited AEs in the 28 days after the second booster: all were unrelated to the treatment. There were no deaths or AEs leading to study discontinuation.

DISCUSSION

A second heterologous NVX-CoV2373 booster in healthy Japanese adults induced more robust anti-SARS-CoV-2 immune responses than the first booster. The second booster was well tolerated. No new safety concerns were identified.

Interdisciplinary Learning Health System Response to Public Vaccine Concerns

In Victoria, Australia, jurisdictional vaccine safety service is conducted by SAEFVIC (Surveillance of Adverse Events Following Vaccination in the Community). SAEFVIC developed a public Vaccine Safety Report (saefvic.online/vaccinesafety) to present key surveillance information. This study applies an interdisciplinary learning health system approach to evaluate the report, taking into consideration public expressions of concern on social media.

The immunogenicity and safety of Group B Streptococcal maternal vaccines: A systematic review

PURPOSE

To systematically review immunogenicity and safety data of maternal group B streptococcal (GBS) vaccines in published clinical trials until July 2023.

METHODS

EMBASE, MEDLINE, Cochrane Library and clinicaltrial.gov. databases were searched for clinical studies that reported immunogenicity and/or safety of GBS vaccine in non-pregnant adults, pregnant women and infants between 1st of January 1996 to 31st of July 2023. Pairs of reviewers independently selected, data extracted, and assessed the risk of bias of the studies. Discrepancies were resolved by consensus. (PROSPERO CRD42020185213).

RESULTS

We retrieved 1472 records from the literature search; 20 studies and 6 sub-studies were included, involving 4440 non-pregnant participants and 1325 pregnant women with their newborns. There was a significantly higher IgG Geometric Mean Concentration (GMC) and IgG placental transfer ratios in vaccinated compared to placebo groups, with peak response 4-8 weeks after vaccination. Placental transfer ratio varied from 0.4 to 1.4 across five studies. The different clinical trials used different assays that limited direct comparison. There were no significant differences in the risk of serious adverse events (adjusted OR 0.73; 95 % CI 0.49-1.07), serious adverse events leading to withdrawal (adjusted OR 0.44; 95 % CI 0.13-1.51), and systemic illness or fever (adjusted OR 1.05; 95 % CI 0.26-4.19) between the vaccine and placebo groups.

CONCLUSIONS

The published clinical trials show significant IgG GMC response in subjects receiving the conjugated capsular polysaccharide and surface subunit protein vaccines compared to placebo. In current clinical trials of experimental GBS maternal vaccines, there have been no observed serious adverse events of special interest directly linked to vaccination.

Nationwide safety surveillance of COVID-19 mRNA vaccines following primary series and first booster vaccination in Singapore

Background

The real-world safety profile of COVID-19 mRNA vaccines remains incompletely elucidated.

Methods

We performed a nationwide post-market safety surveillance analysis in Singapore, on vacinees aged 5 years and older, through mid-September 2022. Observed-over-expected (O/E) analyses were performed to identify potential safety signals among eight shortlisted adverse events of special interest (AESIs): strokes, cerebral venous thrombosis (CVT), acute myocardial infarction, myocarditis/pericarditis, pulmonary embolism, immune thrombocytopenia, convulsions and appendicitis. Self-controlled case series analyses (SCCS) were performed to validate signals of concern, occurring within 42 days of vaccination.

Findings

Elevated risks were observed on O/E analyses for the following AESIs: myocarditis/pericarditis, [rate ratio (RR): 3.66, 95 % confidence interval (95 % CI): 2.71 to 4.94], appendicitis [RR: 1.14 (1.02 to 1.27)] and CVT [RR: 2.11 (1.18 to 3.77)]. SCCS analyses generated corroborative findings: myocarditis/pericarditis, [relative incidence (RI): 6.96 (3.95 to 12.27) at 1 to 7 days post-dose 2], CVT [RI: 4.30 (1.30 to 14.20) at 22 to 42 days post-dose 1] and appendicitis [RI: 1.31 (1.03 to 1.67) at 1 to 7 days post-dose 1]. Booster dose 1 continued to be associated with higher rates of myocarditis/pericarditis on O/E analysis [RR: 2.30, (1.39 to 3.80) and 1.69, (1.11 to 2.59)] at 21- and 42-days post-booster dose 1, respectively. Males aged 12 to 17 exhibited highest risks of both myocarditis/pericarditis [RI: 6.31 (1.36 to 29.3)] and appendicitis [RI: 2.01 (1.12 to 3.64)] after primary vaccination. Similarly, CVT was also predominantly observed in males aged above 50 (11 out of 16 cases), within 42-days of vaccination.

Interpretation

Our data suggest that myocarditis/pericarditis, appendicitis and CVT are associated with primary vaccination using COVID-19 mRNA vaccines. Males at specific ages exhibit higher risks for all three AEs identified. The risk of myocarditis/pericarditis continues to be elevated after booster dose 1.

Adverse events from HPV vaccination in Taiwan

The safety of human papillomavirus (HPV) vaccines has been evaluated continuously in pre-licensure clinical trials, post-marketing surveillance systems, and observational studies. Most studies have found no significant association between serious adverse events and HPV vaccination. However, these studies have focused on Western populations; similar studies focusing on Asian populations are insufficient. Our retrospective cohort study used the HPV-vaccination records of junior high-school adolescent girls aged 12-15 years between 2013 and 2018 in Taiwan's National Immunization Information System and linked them to a registry for beneficiaries in Taiwan's National Health Insurance Database (NHID) to establish the vaccinated group. We selected 19 serious diseases as serious adverse events. We compared the incidence rates of these serious adverse events between the vaccinated group and girls in the same age group population, and we calculated the standardized incidence ratio (SIR) to evaluate the risk of serious adverse events after HPV vaccination. Because of the onset of different types of diseases, we set three periods after the subjects received HPV vaccination: within 3 months, within 1 year, and during the study period (2013-2018). The results showed the incidence rates and the SIRs of 19 selected adverse events. Among the 19 selected serious adverse events, the disease with the highest incidence rate during the study period was fibromyalgia (73.23 cases per million population), and the disease with the lowest incidence rate during the study period was Crohn's disease (0.15 cases per million population). The results showed no statistically significant increases in the risk of 19 selected serious adverse events and indicated no association between HPV vaccination and serious adverse events. Given the benefits and safety of HPV vaccination, our research can reduce concerns about vaccine side effects, inform health policies and improve public and clinician's acceptance of HPV vaccine policy.

Background rates for severe cutaneous reactions in the US: Contextual support for safety assessment of COVID-19 vaccines and novel biologics

The global COVID-19 public health crisis has resulted in extraordinary collaboration to expeditiously develop vaccines and therapeutics. The safety of these biologics is closely monitored by the US Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC). Novel products may have limited safety data, and although serious medical outcomes associated with vaccination are rare, knowledge of background incidence rates of medical conditions in the US population puts reported adverse events (AEs) in perspective for further study. Although relatively minor vaccination skin reactions are common, rare instances of severe delayed hypersensitivity reactions such as erythema multiforme (EM), Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and SJS/TEN overlap syndrome may occur. To aid in the assessment of these events, we performed a literature search in PubMed and Web of Science on the background incidence of EM, SJS, SJS/TEN, and TEN in the US population and on published reports of these conditions occurring post-vaccination. The US background annual incidence rates per million individuals of all ages ranged from 5.3 to 63.0 for SJS, from 0.4 to 5.0 for TEN, and from 0.8 to 1.6 for SJS/TEN. Since these conditions may overlap, some studies reported rates for EM/SJS/TEN combined, however we did not find studies with exclusive EM incidence rates. The published literature, including studies of reports submitted to the FDA/CDC Vaccine Adverse Event Reporting System (VAERS), describes post-vaccination EM, SJS, SJS/TEN and/or TEN as rare occurrences. The vaccines most frequently associated with these conditions were measles, mumps, and rubella; diphtheria, tetanus, and pertussis; and varicella. The majority of VAERS reports of EM, SJS, SJS/TEN, or TEN occurred in children within 30 days of vaccination. This review summarizes background rates of these disorders in the general population and published AEs among vaccine recipients, to support safety surveillance of COVID-19 vaccines and other biologics.

Risk of lymphadenopathy from SARS-CoV-2 vaccination in Korea: a self-controlled case series analysis

OBJECTIVES

To assess the risk of lymphadenopathy following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination.

METHODS

A self-controlled case series design was used to determine whether the risk of lymphadenopathy was higher in the 1-day to 42-day risk interval after coronavirus disease 2019 (COVID-19) vaccination compared to the control period. In addition, subgroup analyses were conducted according to baseline characteristics, time since vaccination, and sensitivity analyses adjusted for the length of the risk interval.

RESULTS

The risk of developing lymphadenopathy in the risk interval (1-42 days) after COVID-19 vaccination compared to the control period was significantly increased, with a relative incidence (RI) of 1.17 (95% confidence interval [CI], 1.17 to 1.18) when the first, second, and third doses were combined. The RI was greater on the day of vaccination (1.47; 95% CI, 1.44 to 1.50). In subgroup analyses by baseline characteristics, a significantly increased risk or trend toward increased risk was observed in most subgroups except for those aged 70 years and older, with a significant increase in risk in younger individuals, those with a Charlson's comorbidity index <5, and those who received mRNA vaccines (mRNA-1273>BNT162b2). Within the 1-day to 42-day post-dose risk period, the relative risk was highest during the 1-day to 7-day post-dose period (1.59; 95% CI, 1.57 to 1.60) compared to the control period, and then the risk declined. In the sensitivity analysis, we found that the longer the risk window, the smaller the RI.

CONCLUSIONS

SARS-CoV-2 vaccination is associated with a statistically significant increase in the risk of lymphadenopathy, and this risk was observed only with mRNA vaccines.

Factors associated with intention for revaccination among patients with adverse events following immunization

OBJECTIVES

Individuals and healthcare providers may be uncertain about the safety of revaccination after an adverse event following immunization (AEFI). We identified factors associated with physician recommendation for revaccination and participant intention to be revaccinated among patients with adverse events following immunization (AEFIs) assessed in the Canadian Special Immunization Clinic (SIC) Network from 2013 to 2019.

METHODS

This prospective observational study included patients assessed in the Canadian Special Immunization Clinic Network from 2013 to 2019 for an AEFI who required additional doses of the vaccine temporally associated with their AEFI. Participants underwent standardized assessment and data collection. Physician recommendations regarding revaccination and participant intent for revaccination were recorded. AEFI impact on daily activities and need for medical attention was captured as low, moderate, high impact and serious (e.g., requiring hospitalization). Multivariable logistic regression analysis identified factors associated with physician recommendation and participant intention for revaccination, controlling for province of assessment.

RESULTS

Physician recommendation was significantly associated with the type of AEFI and AEFI impact. Compared to large local reaction, physician recommendation for revaccination was reduced for immediate hypersensitivity (aOR: 0.24 [95% CI: 0.08-0.76]) and new onset autoimmune disease (aOR: 0.16; 95% CI: 0.04-0.69). Compared to low impact AEFIs, physician recommendation was reduced for moderate (aOR: 0.22 [95% CI: 0.07-0.65]), high impact (aOR: 0.08 [95% CI: 0.02-0.30]), and serious AEFIs (aOR: 0.11 [95% CI: 0.03-0.37]). Participant intention for revaccination was significantly associated with AEFI impact, with reduced odds for high versus low impact AEFIs (aOR: 0.12 [95% CI: 0.04-0.42]).

CONCLUSION

Physicians appear to use AEFI type and impact to guide recommendations while patients use primarily AEFI impact to form intentions for revaccination. The findings may help inform counselling for patients with AEFIs.

COVID-19 vaccine safety in Scotland - background rates of adverse events of special interest

OBJECTIVES

Mass COVID-19 vaccination commenced in December 2020 in Scotland. Monitoring vaccine safety relies on accurate background incidence rates (IRs) for health outcomes potentially associated with vaccination. This study aimed to quantify IRs in Scotland of adverse events of special interest (AESI) potentially associated with COVID-19 vaccination.

STUDY DESIGN AND METHODS

IRs and 95% confidence intervals (CIs) for 36 AESI were calculated retrospectively for the pre-COVID-19 pandemic period (01 January 2015-31 December 2019) and the COVID-19 pandemic period (01 April 2020-30 November 2020), with age-sex stratification, and separately by calendar month and year. Incident cases were determined using International Classification of Diseases-10th Revision (ICD-10)-coded hospitalisations.

RESULTS

Prepandemic population-wide IRs ranged from 0.4 (0.3-0.5 CIs) cases per 100,000 person-years (PYRS) for neuromyelitis optica to 478.4 (475.8-481.0 CIs) cases per 100,000 PYRS for acute renal failure. Pandemic population-wide IRs ranged from 0.3 (0.2-0.5 CIs) cases per 100,000 PYRS for Kawasaki disease to 483.4 (473.2-493.7 CIs) cases per 100,000 PYRS for acute coronary syndrome. All AESI IRs varied by age and sex. Ten AESI (acute coronary syndrome, acute myocardial infarction, angina pectoris, heart failure, multiple sclerosis, polyneuropathies and peripheral neuropathies, respiratory failure, rheumatoid arthritis and polyarthritis, seizures and vasculitis) had lower pandemic than prepandemic period IRs overall. Only deep vein thrombosis and pulmonary embolism had a higher pandemic IR.

CONCLUSION

Lower pandemic IRs likely resulted from reduced health-seeking behaviours and healthcare provision. Higher IRs may be associated with SARS-CoV-2 infections. AESI IRs will facilitate future vaccine safety studies in Scotland.

Thrombocytopenic, thromboembolic and haemorrhagic events following second dose with BNT162b2 and ChAdOx1: self-controlled case series analysis of the English national sentinel cohort

Background

Thrombosis associated with thrombocytopenia was a matter of concern post first and second doses of BNT162b2 and ChAdOx1 COVID-19 vaccines. Therefore, it is important to investigate the risk of thrombocytopenic, thromboembolic and haemorrhagic events following a second dose of BNT162b2 and ChAdOx1 COVID-19 vaccines.

Methods

We conducted a large-scale self-controlled case series analysis, using routine primary care data linked to hospital data, among 12.3 million individuals (16 years old and above) in England. We used the nationally representative Oxford-Royal College of General Practitioners (RCGP) sentinel network database with baseline and risk periods between 8th December 2020 and 11th June 2022. We included individuals who received two vaccine (primary) doses of the BNT162b2 mRNA (Pfizer-BioNTech) and two vaccine doses of ChAdOx1 nCoV-19 (Oxford-AstraZeneca) vaccines in our analyses. We carried out a self-controlled case series (SCCS) analysis for each outcome using a conditional Poisson regression model with an offset for the length of risk period. We reported the incidence rate ratios (IRRs) and 95% confidence intervals (CI) of thrombocytopenic, thromboembolic (including arterial and venous events) and haemorrhagic events, in the period of 0-27 days after receiving a second dose of BNT162b2 or ChAdOx1 vaccines compared to the baseline period (14 or more days prior to first dose, 28 or more days after the second dose and the time between 28 or more days after the first and 14 or more days prior to the second dose). We adjusted for a range of potential confounders, including age, sex, comorbidities and deprivation.

Findings

Between December 8, 2020 and February 11, 2022, 6,306,306 individuals were vaccinated with two doses of BNT162b2 and 6,046,785 individuals were vaccinated with two doses of ChAdOx1. Compared to the baseline, our analysis show no increased risk of venous thromboembolic events (VTE) for both BNT162b2 (IRR 0.71, 95% CI: 0.65-0.770) and ChAdOx1 (IRR 0.91, 95% CI: 0.84-0.98); and similarly there was no increased risk for cerebral venous sinus thrombosis (CVST) for both BNT162b2 (IRR 0.87, 95% CI: 0.41-1.85) and ChAdOx1 (IRR 1.73, 95% CI: 0.82-3.68). We additionally report no difference in IRR for pulmonary embolus, and deep vein thrombosis, thrombocytopenia, including idiopathic thrombocytopenic purpura (ITP), and haemorrhagic events post second dose for both BNT162b2.

Interpretation

Reassuringly, we found no associations between increased risk of thrombocytopenic, thromboembolic and haemorrhagic events post vaccination with second dose for either of these vaccines.

Funding

Data and Connectivity: COVID-19 Vaccines Pharmacovigilance study.

A review of criteria strictness in "Toxicity Grading Scale for Healthy Adult and Adolescent Volunteers Enrolled in Preventive Vaccine Clinical Trials"

To assess safety in vaccine development, stricter grading scales, such as the "Toxicity Grading Scale for Healthy Adult and Adolescent Volunteers Enrolled in Preventive Vaccine Clinical Trials" issued by the U.S. Food and Drug Administration (FDA grading scale), are required. However, concern exists that their strictness may lead to an overestimation of some adverse events (AEs). We analyzed the details of AEs in a phase I clinical trial of a preventive vaccine for infectious diseases. In this trial, we observed the high occurrence of Grade 1 or greater AEs in hemoglobin changes from baseline value, and hypernatremia, and hypokalemia by FDA grading scale. The range considered as non-AE according to the FDA grading scale shifted or became narrower when compared to reference intervals, especially for a Japanese cohort. For sodium grading, the criterion for hypernatremia was around 2 to mEq/L lower than the upper limit of most standards in several countries. Also, the criterion for hypokalemia was around 0.2 mEq/L higher than the lower limit of most standards. Regarding a decrease in hemoglobin from baseline, the criterion of "any decrease" used for a Grade 1 AE was too strict and we suggest this be omitted. Upper and lower limits of AE criteria for sodium and potassium should be equal to, or 10-20% above, the reference interval consistent with other toxicities determined by laboratory tests. Consideration should be given to the issues surrounding the criteria that determine AEs before conducting clinical trials.

Relapsing myocarditis following initial recovery of post COVID-19 vaccination in two adolescent males - Case reports

Whilst there has been significant public health benefits associated with global use of COVID-19 spike protein vaccines, potential serious adverse events following immunization have been reported. Acute myocarditis is a rare complication of COVID19 vaccines and often it is self-limiting. We describe two cases experiencing recurrent myocarditis following mRNA COVID-19 vaccine despite a prior episode with full clinical recovery. Between September 2021-September 2022 we observed two male adolescents with recurrent myocarditis related to mRNA-based-COVID19 vaccine. During the first episode both patients presented with fever and chest pain few days after their second dose of BNT162b2 mRNA Covid-19 Vaccine (Comirnaty®). The blood exams showed increased cardiac enzymes. In addition, complete viral panel was run, showing HHV7 positivity in a single case. The left ventricular ejection fraction (LVEF) was normal at echocardiogram but cardiac magnetic resonance scanning (CMR) was consistent with myocarditis. They were treated with supportive treatment with full recovery. The 6 months follow-up demonstrated good clinical conditions with normal cardiological findings. The CMR showed persistent lesions in left ventricle 's wall with LGE. After some months the patients presented at emergency department with fever and chest pain and increased cardiac enzymes. No decreased LVEF was observed. The CMR showed new focal areas of edema in the first case report and stable lesions in the second one. They reached full recovery with normalization of cardiac enzymes after few days. These case reports outline the need of strict follow-up in patients with CMR consistent with myocarditis after mRNA-based-COVID19 vaccine. More efforts are necessary to depict the underlying mechanisms of myocarditis after SARS-CoV2 vaccination to understand the risk of relapsing and the long-term sequelae.

Adverse Events Following Immunization- The Known Unknowns and Black Box : Based on 10th Dr. I. C. Verma Excellence Award for Young Pediatricians Delivered as Oration on 9th Oct. 2022

Although vaccines are one of the most rigorously tested biological products, the safety concerns persist globally. The vaccine safety concerns linked to measles, pentavalent and human papillomavirus (HPV) vaccines have affected the vaccine coverage significantly in past. While surveillance of adverse events following immunization (AEFI) is part of the national immunization program mandate, it suffers from challenges and biases related to reporting, completeness, and quality. Some conditions of concern, termed as adverse events of special interest (AESI) following vaccination, mandated specialised studies to prove/disprove the association. The AEFIs/AESIs are usually caused by one of the four pathophysiologic mechanisms, but for several AEFIs/AESIs, the exact pathophysiology remains elusive. For the causality assessment of AEFIs, a systematic process with checklists and algorithm are followed to classify into one of the four causal association categories. While the causal association primarily banks on epidemiological observations for several AEFIs, the emerging evidences indicate roles of underlying genetic, gender, age and other pro-inflammatory risk factors for AEFIs and AESIs. The emerging evidences suggest role of antigenic mimicry, autoantibody(ies) and underlying genetic susceptibility for the AEFIs/AESIs. The uncertainty about the frequency, profile, interval, and severity of AEFIs/AESIs and variations across the population, ambiguity about the exact pathophysiology mechanism, absence of definite markers, suggest a possible black box effect of the vaccines. Unless these unanswered questions concerning the AEFIs/AESIs are addressed appropriately and communicated to the stakeholders (professionals, care providers, beneficiaries, general public and media), the anti-vaccine movement shall keep challenging the vaccine and vaccination program.

Myocarditis following COVID-19 mRNA vaccinations: Twin and sibling case series

ImportanceMyocarditis and myopericarditis are well described adverse events of special interest (AESI) following COVID-19 vaccinations. Whilst the aetiology is still being investigated; there is evidence that genetic predisposition may be a risk factor for the development of myocarditis. Furthermore, hormones are thought to contribute to sex-specific differences in myocarditis, skewed toward a larger risk in adolescent males.

Objective

This unique sibling case series may help highlight potential mechanisms and prognostic factors in the development of myocarditis following COVID-19 vaccination in adolescent males. In this context, twin and familial studies provide a unique epidemiological perspective to investigate the interplay between genetic predisposition and other factors.

Participants

Observational case series of all siblings reported to SAEFVIC with chest pain following COVID-19 vaccinations in Victoria, Australia.

Exposure

mRNA vaccination (Comirnaty BNT162b2 COVID-19 (Pfizer-BioNTech) and Spikevax mRNA-1273 (Moderna).

Findings

Our case series comprises 6 young males; two sets of monozygotic twins and one set of fraternal brothers following reports of chest pain associated with COVID-19 mRNA vaccination. Five patients were diagnosed with myocarditis as per Brighton Collaboration Criteria (Level 2). The remaining sibling, who did not have myocarditis, was subsequently diagnosed with pubertal delay.

Conclusions

Understanding the genetic and hormonal risk factors and aetiology for myocarditis associated with COVID-19 vaccines is paramount. Further evaluation of specific genetic targets or biomarkers is required to understand the implications of population vaccine policy, particularly for adolescent and young adult males at highest risk for this AESI.

Reliability and comprehensiveness of YouTube videos about the COVID-19 vaccine in pregnancy

Online information influences health care decisions and may contribute to vaccine hesitancy among pregnant individuals. We assessed the quality (reliability and comprehensiveness) of YouTube videos about COVID-19 vaccination in pregnancy. We systematically identified videos and recorded video information and quality. 137 videos were reviewed. Comments, likes, dislikes, duration, reliability, and content scores differed between sources. Videos were low quality overall, but videos produced by medical sources tended to be higher quality. Quality was positively correlated with duration, but not views.

COVID-19 vaccine safety inquiries to the centers for disease control and prevention immunization safety office

BACKGROUND

Following the authorization and recommendations for use of the U.S. COVID-19 vaccines, the Centers for Disease Control and Prevention (CDC)'s Immunization Safety Office (ISO) responded to inquiries and questions from public health officials, healthcare providers, and the general public on COVID-19 vaccine safety.

METHODS

We describe COVID-19 vaccine safety inquiries, by topic, received and addressed by ISO from December 1, 2020-August 31, 2022.

RESULTS

Of the 1978 COVID-19 vaccine-related inquiries received, 1655 specifically involved vaccine safety topics. The most frequently asked-about topics included deaths following vaccination, myocarditis, pregnancy, and reproductive health outcomes, understanding or interpreting data from the Vaccine Adverse Event Reporting System (VAERS), and thrombosis with thrombocytopenia syndrome.

CONCLUSIONS

Inquiries about vaccine safety generally reflect issues that receive media attention. ISO will continue to monitor vaccine safety inquiries and provide accurate and timely information to healthcare providers, public health officials, and the general public.

Immunogenicity and safety of a fourth homologous dose of NVX-CoV2373

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants has significantly reduced the efficacy of some approved vaccines. A fourth dose of NVX-CoV2373 (5 µg SARS-CoV-2 recombinant spike [rS] protein + 50 µg Matrix-M™ adjuvant; Novavax, Gaithersburg, MD) was evaluated to determine induction of cross-reactive antibodies to variants of concern. A phase II randomized study (NCT04368988) recruited participants in Australia and the United States to assess a primary series of NVX-CoV2373 followed by two booster doses (third and fourth doses at 6-month intervals) in adults 18-84 years of age. The primary series was administered when the SARS-CoV-2 ancestral strain was prevalent and the third and fourth doses while the Alpha and Delta variants were prevalent in AUS and US. Local/systemic reactogenicity was assessed the day of vaccination and for 6 days thereafter. Unsolicited adverse events (AEs) were reported. Immunogenicity was measured before, and 14 days after, fourth dose administration, using anti-spike serum immunoglobulin G (IgG) and neutralization assays against ancestral SARS-CoV-2 strain and Omicron sublineages. Among 1283 enrolled participants, 258 were randomized to receive the two-dose primary series, of whom 104 received a third dose, and 45 received a fourth dose of NVX-CoV2373. The incidence of local/systemic reactogenicity events increased after the first three doses of NVX-CoV2373 and leveled off after dose 4. Unsolicited AEs were reported in 9 % of participants after dose 4 (none of which were severe or serious). Anti-rS IgG levels and neutralization antibody titers increased following booster doses to a level approximately four-fold higher than that observed after the primary series, with a progressively narrowed gap in response between the ancestral strain and Omicron BA.5. A fourth dose of NVX-CoV2373 enhanced immunogenicity for ancestral and variant SARS-CoV-2 strains without increasing reactogenicity, indicating that updates to the vaccine composition may not be currently warranted.

Erratum: Factors influencing scar formation following Bacille Calmette-Guérin (BCG) vaccination

[This corrects the article DOI: 10.1016/j.heliyon.2023.e15241.].

Assessing vaccine safety during a pandemic: Recent experience and lessons learned for the future

During the roll out of vaccines during a pandemic, questions regarding vaccine safety often arise. This was surely true during the SARS-CoV-2 pandemic. Different tools and capabilities exist during the pre-authorization phase and post introduction each with its strengths and limitations. Here we review the various tools and their strengths and limitations and discuss what functioned well in high income settings and the limitations that unequal vaccine safety pharmacovigilance capacity imposed upon middle and low income countries.

Considerations for unblinding individual study participants during vaccine trials

Premature unblinding of individual participants is rarely reported in publications, but such unblinding can disrupt vaccine trials by causing worry and drop-out of other participants or "pseudo unblinding," in which participants or investigators over-interpret certain symptoms as being related to receiving an investigational product. This review summarizes appropriate reasons for unblinding in vaccine trials. Regulatory guidance could be improved by distinguishing guidance for vaccine trials from drug trials, with the recognition that unblinding individual participants in vaccine studies is rarely needed for management of adverse events following immunization.

Background incidence rates of selected adverse events of special interest (AESI) to monitor the safety of COVID-19 vaccines

BACKGROUND

Determining background rates of medical conditions identified as adverse events of special interest (AESI) that may occur following COVID-19 vaccination is important for contextualising and investigating potential vaccine safety signals.

METHODS

We conducted a retrospective population-based cohort study using linked emergency department, hospitalisation and death data for 2017 and 2018 from Australia's most populous state, New South Wales. Incident cases of select neurological conditions, arterial or venous thromboembolic conditions, secondary thrombocytopenia, myocarditis/pericarditis, and unique events of anaphylaxis and generalised convulsions were identified using internationally agreed upon diagnostic (ICD-10) codes. State-specific rates per 100,000 person-years were calculated, with further stratification by age group and sex where clinically relevant to the condition, and the number of expected cases nationally in one and 6 weeks was estimated.

RESULTS

Background rates of selected neurological conditions were low with the exception of generalised convulsions for which 1,599-1,872 cases were estimated nationally in a 1-week period in the absence of vaccination. Using a narrow case definition, rates of Guillain-Barré Syndrome (3.9 per 100,000 person-years) were higher than international rates reported elsewhere. Thromboembolic and cerebral venous sinus thrombosis event rates increased with age. Myocarditis occurred more commonly in males, and was highest in males aged 18-24 years, with an estimated 1-4 cases expected nationally in a 1-week period.

CONCLUSIONS

Using routinely collected linked healthcare data provides localised estimates of background rates of new onset or periodic AESI which enables rapid estimation of observed-versus-expected rates of events reported following COVID-19 vaccination. This Australian-specific analysis contributes AESI background rates which can be compared with those from other countries to enhance understanding of geographic variability in the frequency of specific AESI in the absence of vaccination, and can be utilised for signal detection during program implementation.

Systemic reactogenicity following homologues and heterologous prime-boost AZD1222 and BNT162b2 COVID-19 vaccination of 2862 healthcare workers compared with an unvaccinated population

During spring 2021, AZD1222 and BNT162b2 were used as prime and BNT162b2 as booster COVID-19 vaccines in Denmark. We obtained self-reported information on systemic reactogenicity day-by-day during two weeks for 2862 healthcare workers vaccinated with heterologous AZD1222 + BNT162b2 or homologous BNT162b2 + BNT162b2 regimens and compared prevalences of symptoms with unvaccinated healthcare workers. We found comparable systemic reactogenicity during the first week in the two vaccine regimens and no reactogenicity during the second week. Most of the symptoms returned to a level equal to the control population four days after booster vaccination.

Factors influencing scar formation following Bacille Calmette-Guérin (BCG) vaccination

The prevalence of scar formation following Bacille Calmette-Guérin (BCG) vaccination varies globally. The beneficial off-target effects of BCG are proposed to be stronger amongst children who develop a BCG scar. Within an international randomised trial ('BCG vaccination to reduce the impact of coronavirus disease 2019 (COVID-19) in healthcare workers'; BRACE Trial), this nested prospective cohort study assessed the prevalence of and factors influencing scar formation, as well as participant perception of BCG scarring 12 months following vaccination . Amongst 3071 BCG-recipients, 2341 (76%) developed a BCG scar. Scar prevalence was lowest in Spain and highest in UK. Absence of post-injection wheal (OR 0.4, 95%CI 0.2-0.9), BCG revaccination (OR 1.7, 95%CI 1.3-2.0), female sex (OR 2.0, 95%CI 1.7-2.4), older age (OR 0.4, 95%CI 0.4-0.5) and study country (Brazil OR 1.6, 95%CI 1.3-2.0) influenced BCG scar prevalence. Of the 2341 participants with a BCG scar, 1806 (77%) did not mind having the scar. Participants more likely to not mind were those in Brazil, males and those with a prior BCG vaccination history. The majority (96%) did not regret having the vaccine. Both vaccination-related (amenable to optimisation) and individual-related factors affected BCG scar prevalence 12 months following BCG vaccination of adults, with implications for maximising the effectiveness of BCG vaccination.

Vaccinomics: A scoping review

BACKGROUND

This scoping review summarizes a key aspect of vaccinomics by collating known associations between heterogeneity in human genetics and vaccine immunogenicity and safety.

METHODS

We searched PubMed for articles in English using terms covering vaccines routinely recommended to the general US population, their effects, and genetics/genomics. Included studies were controlled and demonstrated statistically significant associations with vaccine immunogenicity or safety. Studies of Pandemrix®, an influenza vaccine previously used in Europe, were also included, due to its widely publicized genetically mediated association with narcolepsy.

FINDINGS

Of the 2,300 articles manually screened, 214 were included for data extraction. Six included articles examined genetic influences on vaccine safety; the rest examined vaccine immunogenicity. Hepatitis B vaccine immunogenicity was reported in 92 articles and associated with 277 genetic determinants across 117 genes. Thirty-three articles identified 291 genetic determinants across 118 genes associated with measles vaccine immunogenicity, 22 articles identified 311 genetic determinants across 110 genes associated with rubella vaccine immunogenicity, and 25 articles identified 48 genetic determinants across 34 genes associated with influenza vaccine immunogenicity. Other vaccines had fewer than 10 studies each identifying genetic determinants of their immunogenicity. Genetic associations were reported with 4 adverse events following influenza vaccination (narcolepsy, GBS, GCA/PMR, high temperature) and 2 adverse events following measles vaccination (fever, febrile seizure).

CONCLUSION

This scoping review identified numerous genetic associations with vaccine immunogenicity and several genetic associations with vaccine safety. Most associations were only reported in one study. This illustrates both the potential of and need for investment in vaccinomics. Current research in this field is focused on systems and genetic-based studies designed to identify risk signatures for serious vaccine reactions or diminished vaccine immunogenicity. Such research could bolster our ability to develop safer and more effective vaccines.

Risk of carditis after three doses of vaccination with mRNA (BNT162b2) or inactivated (CoronaVac) covid-19 vaccination: a self-controlled cases series and a case-control study

Background

Large-scale comparative research exploring the risk after the third dose and after inactivated covid-19 vaccination is limited. This study aimed to assess the risk of carditis following three doses of BNT162b2 or CoronaVac.

Methods

We conducted a self-controlled case series (SCCS) and a case-control study using electronic health and vaccination records in Hong Kong. Carditis incidents within 28 days of covid-19 vaccination were included as cases. In the case-control study, up to 10 hospitalized controls were selected with stratified probability sampling by age, sex, and hospital admission (±1 day). The incidence rate ratios (IRRs) were reported from conditional Poisson regressions for SCCS, and adjusted odds ratios (ORs) were reported from multivariable logistic regressions.

Findings

A total of 8,924,614 doses of BNT162b2 and 6,129,852 doses of CoronaVac were administered from February 2021 to March 2022. The SCCS detected increased carditis risks after BNT162b2: 4.48 (95%confidence interval [CI]:2.99-6.70] in 1-14 days and 2.50 (95%CI:1.43-4.38) in 15-28 days after first dose; 10.81 (95%CI:7.63-15.32) in 1-14 days and 2.95 (95%CI:1.82-4.78) in 15-28 days after second dose; 4.72 (95%CI:1.40-15.97) in 1-14 days after third dose. Consistent results were observed from the case-control study. Risks were specifically found in people aged below 30 years and males. No significant risk increase was observed after CoronaVac in all primary analyses.

Interpretations

We detected increased carditis risks within 28 days after all three doses of BNT162b2 but the risk after the third doses were not higher than that of the second dose when compared with baseline period. Continuous monitoring of carditis after both mRNA and inactivated covid-19 vaccines is needed.

Funding

: This study was funded by Hong Kong Health Bureau (COVID19F01).

Safety of co-administration of mRNA COVID-19 and seasonal inactivated influenza vaccines in the vaccine adverse event reporting system (VAERS) during July 1, 2021-June 30, 2022

BACKGROUND

COVID-19 vaccines may be co-administered with other recommended vaccines, including seasonal influenza vaccines. However, few studies have evaluated the safety of co-administration of mRNA COVID-19 and seasonal influenza vaccines.

OBJECTIVE

To describe reports to the Vaccine Adverse Event Reporting System (VAERS) after co-administration of mRNA COVID-19 and seasonal influenza vaccines.

METHODS

We searched the VAERS database for reports of adverse events (AEs) following co-administration of mRNA COVID-19 and seasonal influenza vaccines and following a first booster dose mRNA COVID-19 vaccine alone, during July 1, 2021-June 30, 2022. We assessed the characteristics of these reports and described the most frequently reported MedDRA preferred terms (PTs). Clinicians reviewed available medical records for serious reports and reports of adverse events of special interest (AESI) and categorized the main diagnosis by system organ class.

RESULTS

From July 1, 2021 through June 30, 2022, VAERS received 2,449 reports of adverse events following co-administration of mRNA COVID-19 and seasonal influenza vaccines. Median age of vaccinees was 48 years (IQR: 31, 66); 387 (15.8%) were classified as serious. Most reports (1,713; 69.3%) described co-administration of a first booster dose of an mRNA COVID-19 vaccine with seasonal influenza vaccine. The most common AEs among non-serious reports were injection site reactions (193; 14.5%), headache (181; 13.6%), and pain (171; 12.8%). The most common AEs among reports classified as serious were dyspnea (38; 14.9%), COVID-19 infection (32; 12.6%), and chest pain (27; 10.6%).

DISCUSSION

This review of reports to VAERS following co-administration of mRNA COVID-19 and seasonal influenza vaccines did not reveal any unusual or unexpected patterns of AEs. Increased reporting of certain events (e.g., COVID-19 disease) was expected. CDC will continue to monitor the safety of co-administration of mRNA COVID-19 and seasonal influenza vaccines, including co-administration involving bivalent mRNA COVID-19 booster vaccines that have been recommended for people ages ≥ 6 months in the United States.

Incident autoimmune conditions among males receiving quadrivalent human papillomavirus vaccine in the United States

BACKGROUND

The potential for vaccines to induce autoimmunity has been the subject of considerable investigation and autoimmune induction remains a common focus for vaccine safety research. This study assessed the risk of new onset autoimmune conditions among males receiving the 4-valent human papillomavirus (HPV) vaccine (4vHPV).

METHODS

Within a US health insurance claims database, we formed a cohort of male 4vHPV vaccine recipients between 2009 and 2016, along with a propensity score matched cohort of males who did not receive the 4vHPV vaccine. The study outcome was new onset autoimmune conditions (20 separate conditions) within four categories (rheumatologic/hematologic, gastroenterologic, endocrinologic and neurologic/ophthalmalogic). Outcomes identified using diagnosis codes were adjudicated through medical record review. Incidence rates (per 1,000 person-years) were estimated for the vaccinated and unvaccinated groups along with rate ratios (RRs).

RESULTS

There were 65,606 males receiving at least one dose of 4vHPV vaccine, and 55,670 were matched to a comparator. The matched 4vHPV vaccine cohort provided 35 confirmed cases among 39,735 person-years, for an incidence rate of 0.88 (95% CI: 0.61-1.23), while the comparator cohort provided 47 confirmed cases among 58,215 person-years, an incidence rate of 0.81 (0.59-1.07), a RR of 1.09 (0.70-1.69). The RR within categories was 0.49 (0.10-2.42) for rheumatologic/hematologic, 1.26 (0.58-2.71) for gastroenterologic, 1.11 (0.61-2.02) for endocrinologic and 1.46 (0.21-10.40) for neurologic.

CONCLUSIONS

The incidence of autoimmune conditions among males receiving the 4vHPV vaccine was similar to that among unvaccinated males. These results are consistent with other studies that have assessed autoimmunity with the 4vHPV vaccine.

Safety of 9-valent human papillomavirus vaccine administered to males and females in routine use

BACKGROUND

The nine-valent human papillomavirus vaccine (HPV9, Gardasil®9) was licensed in the USA in December 2014. This study was a multiyear post-licensure study to assess HPV9 safety following routine administration.

METHODS

This retrospective cohort study compared the risk of emergency department visits and hospitalizations during the interval soon after vaccination with risk during a later interval. Kaiser Permanente Northern California (KPNC) members aged ≥ 9 years who received ≥ 1 HPV9 dose between 10/1/2015-9/30/2017 were included. Outcomes were grouped into predefined diagnostic categories. We compared the odds of events in postvaccination risk intervals (days 0-14, days 1-60) with odds of events during control intervals (days 61-75, days 61-120) using conditional logistic regression. We characterized prespecified events on the day of vaccination (allergic reaction and syncope) and all deaths in the study period.

RESULTS

The study included 215,965 individuals receiving ≥ 1 dose of HPV9, of whom 140,628 had no prior HPV vaccination. We observed similar numbers of males and females and racial/ethnic diversity consistent with the underlying population. At first dose median age was 12-13 years and 77% received ≥ 1 concomitant vaccine. Eighteen event categories were significantly elevated, including skin disorders (odds ratio [OR] 1.88, 95% confidence interval [CI] 1.00, 3.53) and ill-defined conditions (OR 1.36, 95% CI 1.13, 1.64; category includes abdominal pain, allergic reactions, syncope, etc.). On review, most findings were previously known, preceded vaccination, or had other causes. Allergic reactions and syncope at vaccination were infrequent but many were potentially related. No deaths (n = 37) were considered related to HPV9 and were consistent with the background rate.

CONCLUSIONS

We did not identify new safety concerns related to HPV9. The results are consistent with the HPV9 safety profile as established from previous studies/surveillance.

REGISTRATION

European Network of Centres for Pharmacoepidemiology and Pharmacovigilance (EUPAS13151, protocol V503-028).

Safety of concomitant administration of inactivated hepatitis A vaccine with other vaccines in children under 16 years old in post-marketing surveillance

BACKGROUND

Concomitant administration refers to the receipt of two or more vaccines during a single healthcare encounter, which is an efficient way to increase vaccination coverage in children. However, the post-marketing safety studies of concomitant administration are scarce. Inactivated hepatitis A vaccine (Healive®) has been used widely in China and other countries for more than a decade. We aimed to explore the safety of Healive® co-administered with other vaccines compared to Healive® alone in children under 16 years old.

METHODS

We retrieved Adverse Events Following Immunization (AEFI) cases and vaccination doses of Healive® during 2020-2021 in Shanghai, China. The AEFI cases were divided into concomitant administration group and Healive® alone group. We used administrative data on vaccine doses as denominators to calculate and compare crude reporting rates between groups. We also compared baseline gender and age distribution, clinical diagnoses, and time interval from vaccination to onset of symptoms between groups.

RESULTS

A total 319,247 doses of inactivated hepatitis A vaccine (Healive®) were used and 1,020 AEFI cases (319.50 per million doses) associated with Healive® were reported during 2020-2021 in Shanghai. There were 259,346 doses concomitantly administered with other vaccines and 830 AEFI cases (320.04 per million doses) were reported. There were 59,901 doses of Healive® that vaccinated alone, with 190 AEFI cases (317.19 per million doses). There was only one case with serious AEFI in concomitant administration group, with a rate of 0.39 per million doses. Reported rates of AEFI cases were similar between groups in general (p > 0.05).

CONCLUSION

Concomitant administration of inactivated hepatitis A vaccine (Healive®) with other vaccines has a similar safe profile as Healive® alone.

Safety and efficacy of tuberculosis vaccine candidates in low- and middle-income countries: a systematic review of randomised controlled clinical trials

BACKGROUND

Tuberculosis (TB) remains a leading cause of death worldwide, with 98% of cases occurring in low- and middle-income countries (LMICs). The only vaccine licenced for the prevention of TB has limited protection for adolescents, adults and vulnerable populations. A safe and effective vaccine for all populations at risk is imperative to achieve global elimination of TB. We aimed to systematically review the efficacy and safety of TB vaccine candidates in late-phase clinical trials conducted in LMICs.

METHODS

Medline, Embase, CENTRAL, PubMed, Clinicaltrials.gov and Greylit.org were searched in June 2021 to identify phase 2 or later clinical randomised controlled trials that report the efficacy or safety (adverse events) of TB vaccine candidates with participants of any age living in an LMIC. TB vaccine candidates listed in the 2020 WHO Global TB Report were eligible for inclusion aside from BCG revaccination. Trials were excluded if all participants had active TB at baseline. Two reviewers independently assessed papers for eligibility, and for bias and quality using the Risk of Bias 2 tool and GRADE guidelines, respectively. We report efficacy rates and frequencies of adverse events from each included trial where available and qualitatively synthesise the findings.

RESULTS

Thirteen papers representing eleven trials met our inclusion criteria. Seven vaccine candidates were reviewed across seven countries: M72/AS01, RUTI, VPM1002, H56:IC31, MTBVAC, DAR-901 and ID93 + GLA-SE. Two trials reported on efficacy: an efficacy rate of 54% (95% CI 11.5, 76.2) was reported for M72/AS01 in adults with latent TB and 3% (95% CI -13.9, 17.7) for DAR-901 in healthy adolescents. However, the latter trial was underpowered. All vaccine candidates had comparable occurrences of adverse events between treatment arms and demonstrated acceptable safety profiles; though, RUTI resulted in one serious complication in a person living with HIV. M72/AS01 was the only vaccine considered safe across a diverse group of people including people living with HIV or latent TB and healthy infants and adolescents.

CONCLUSION

Further efficacy trials for M72/AS01 are warranted to include additional populations at risk where safety has been demonstrated. Further safety trials are needed for the remaining vaccine candidates to confirm safety in vulnerable populations.

Comparative frequency of specified adverse events following Vero cell culture-derived Japanese encephalitis and Vi capsular polysaccharide typhoid vaccines in U.S. military personnel, July 2011-August 2019

Vero cell culture-derived Japanese encephalitis (JE) vaccine (JE-VC; Ixiaro) was approved in the United States in 2009. The previous JE vaccine, an inactivated mouse brain-derived vaccine, had been associated with rare, but serious, allergic and neurologic adverse events (AE). Studies and AE surveillance have supported JE-VC's safety, but one evaluation among military personnel found elevated hypersensitivity and neurologic AE rates. However, co-administration of multiple vaccines to some personnel might have affected results. We retrospectively compared rates of hypersensitivity and neurologic AEs within 28 days following vaccination of military personnel with JE-VC or parenteral Vi capsular polysaccharide typhoid vaccine administered without other vaccines from July 1, 2011, through August 31, 2019. Rates of most events were similar between the vaccines. Only delayed hypersensitivity reactions occurred more frequently following JE-VC (rate ratio: 4.2, 95 % CI 1.2-15.3; p = 0.03), but rates were low for both vaccines. These results support JE-VC's safety.

Spontaneous reports of primary ovarian insufficiency after vaccination: A review of the vaccine adverse event reporting system (VAERS)

BACKGROUND

Since 2012, reports of primary ovarian insufficiency (POI) temporally associated with receipt of human papillomavirus (HPV) vaccine have been published leading to questions about a potential causal association. A Vaccine Safety Datalink study did not find an increased risk for POI after vaccination. We reviewed the Vaccine Adverse Event Reporting System (VAERS) to describe POI reports.

METHODS

We searched VAERS, a U.S. passive surveillance system, for domestic POI reports received from 01/01/1990 to 12/31/2017 after any vaccination. The search used both Medical Dictionary for Regulatory Activity Preferred Terms and a text-based search for POI and its symptoms. All reports were reviewed, and the American College of Obstetricians and Gynecologists (ACOG) guidelines for POI diagnosis were applied. Data mining for disproportionate reporting was conducted.

RESULTS

Six hundred fifty-two reports met the search criteria and clinical review identified 19 POI reports. Most reports (n = 16) were received between 2013 and 2017. The median age at vaccination was 14.5 years (range 10-25 years) and the median interval between first dose of vaccination and reporting the event to VAERS was 43 months (range 4-132 months; mean 59.6 months). Four reports met ACOG diagnostic criteria; one with an underlying cause (47XXX chromosomal abnormality) reported. Eleven reports documented menstrual irregularity ≥ 3 months; 5 had ≥ 1 laboratory test result used to diagnose POI. Eighteen of 19 reports described receipt of HPV vaccine with or without other vaccines. Other vaccines reported were meningococcal conjugate vaccine, hepatitis A, varicella and tetanus toxoid, reduced diphtheria toxoid and acellular pertussis. Disproportionate reporting was found for three relevant coding terms after HPV vaccination.

CONCLUSIONS

POI is rarely reported to VAERS. Most reports contained limited diagnostic information and were submitted after published cases of POI following HPV vaccination. Results of our review do not suggest a safety concern.

Cox regression using a calendar time scale was unbiased in simulations of COVID-19 vaccine effectiveness & safety

BACKGROUND

Observational studies on corona virus disease 2019 (COVID-19) vaccines compare event rates in vaccinated and unvaccinated person time using Poisson or Cox regression. In Cox regression, the chosen time scale needs to account for the time-varying incidence of severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) infection and COVID-19 vaccination.We aimed to quantify bias in person-time based methods, with and without adjustment for calendar time, using simulations and empirical data analysis.

METHODS

We simulated 500,000 individuals who were followed for 365 days, and a point exposure resembling COVID-19 vaccination (cumulative incidence 80%). We generated an effectiveness outcome, emulating the incidence of severe acute respiratory syndrome corona virus 2 infection in Denmark during 2021 (risk 10%), and a safety outcome with seasonal variation (myocarditis, risk 1/5,000). Incidence rate ratios (IRRs) were set to 0.1 for effectiveness and 5.0 for safety outcomes. IRRs and hazard ratios (HRs) were estimated using Poisson and Cox regression with a time under observation scale, and a calendar time scale. Bias was defined as estimated IRR or HR-true IRR. Further, we obtained estimates for both outcomes using data from the Danish health registries.

RESULTS

Unadjusted IRRs (bias_effectivenes +0.16; bias_safety -2.09) and HRs estimated using a time-under-observation scale (+0.28;-2.15) were biased. Adjustment for calendar time reduced bias in Cox (+0.03; +0.33) and Poisson regression (0.00; -0.28). Cox regression using a calendar time scale was least biased (0.00, +0.12). When analyzing empirical data, adjusted Poisson and Cox regression using a calendar time scale yielded estimates in accordance with existing evidence.

CONCLUSION

Lack of adjustment for the time-varying incidence of COVID-19 related outcomes may severely bias estimates.