COVID-19 vaccines and adverse events of special interest: A multinational Global Vaccine Data Network (GVDN) cohort study of 99 million vaccinated individuals

BACKGROUND

The Global COVID Vaccine Safety (GCoVS) Project, established in 2021 under the multinational Global Vaccine Data Network™ (GVDN®), facilitates comprehensive assessment of vaccine safety. This study aimed to evaluate the risk of adverse events of special interest (AESI) following COVID-19 vaccination from 10 sites across eight countries.

METHODS

Using a common protocol, this observational cohort study compared observed with expected rates of 13 selected AESI across neurological, haematological, and cardiac outcomes. Expected rates were obtained by participating sites using pre-COVID-19 vaccination healthcare data stratified by age and sex. Observed rates were reported from the same healthcare datasets since COVID-19 vaccination program rollout. AESI occurring up to 42 days following vaccination with mRNA (BNT162b2 and mRNA-1273) and adenovirus-vector (ChAdOx1) vaccines were included in the primary analysis. Risks were assessed using observed versus expected (OE) ratios with 95 % confidence intervals. Prioritised potential safety signals were those with lower bound of the 95 % confidence interval (LBCI) greater than 1.5.

RESULTS

Participants included 99,068,901 vaccinated individuals. In total, 183,559,462 doses of BNT162b2, 36,178,442 doses of mRNA-1273, and 23,093,399 doses of ChAdOx1 were administered across participating sites in the study period. Risk periods following homologous vaccination schedules contributed 23,168,335 person-years of follow-up. OE ratios with LBCI > 1.5 were observed for Guillain-Barré syndrome (2.49, 95 % CI: 2.15, 2.87) and cerebral venous sinus thrombosis (3.23, 95 % CI: 2.51, 4.09) following the first dose of ChAdOx1 vaccine. Acute disseminated encephalomyelitis showed an OE ratio of 3.78 (95 % CI: 1.52, 7.78) following the first dose of mRNA-1273 vaccine. The OE ratios for myocarditis and pericarditis following BNT162b2, mRNA-1273, and ChAdOx1 were significantly increased with LBCIs > 1.5.

CONCLUSION

This multi-country analysis confirmed pre-established safety signals for myocarditis, pericarditis, Guillain-Barré syndrome, and cerebral venous sinus thrombosis. Other potential safety signals that require further investigation were identified.

Assessment of adherence to pre-vaccination precautions and AEFI reporting practices during BCG vaccination in 4 hospitals in Ghana

The BCG vaccine, like all other vaccines, is associated with adverse events following immunization (AEFI). Reducing the incidence of AEFI is crucial in reposing confidence in BCG vaccination and reducing hesitancy associated with the vaccine. This requires safety precautions before and during vaccinations, as well as reporting AEFIs after vaccination. This study assessed the adherence of health-care professionals to pre-vaccination precautions and adverse events following immunization (AEFI) reporting practices during BCG vaccination in four hospitals in Ghana. It is hoped that the findings of the study will serve as a baseline to identify gaps for further studies to generate a stronger evidence for policy formulation aimed at improving BCG vaccine safety in Ghana and other tuberculosis endemic countries. A cross-sectional study design was employed, and Statistical Package for Social Sciences, IBM® SPSS version 25 (SPSS Inc. USA) software was used for analysis. Chi-square and binary logistic regression tests were used to test the association between categorical variables and predictors of adherence to pre-BCG vaccination precautions, respectively, and a p-value of <.05 was considered statistically significant. The AEFIs commonly reported by mothers included abscess, injection site pain, injection site redness, fever, rash, muscle weakness, diarrhea, vomiting, coughing and rhinitis. Ninety-three participants (73.2%) were adherent to pre-BCG vaccination precautions. Ninety-two participants (72.4%) informed mothers to report all AEFIs encountered. Adherence to pre-BCG vaccination precautions and AEFI reporting were generally good; however, there is still room for improvement.

Delayed adverse events following COVID-19 vaccination in patients with systemic sclerosis and other autoimmune diseases: a substudy of the COVAD-2 cohort

Data on short-term safety of COVID-19 vaccination in patients with systemic sclerosis (SSc) were explored previously in the first COVID-19 vaccination in autoimmune diseases (COVAD) survey conducted in 2021. However, delayed adverse events (ADEs) (occurring > 7 days post-vaccination) are poorly characterized in these patients with SSc. In this study, we analysed delayed COVID-19 vaccine-related ADEs among patients with SSc, other systemic autoimmune and inflammatory disorders (SAIDs) and healthy controls (HCs) using data from the second COVAD study conducted in 2022. The COVAD-2 study was a cross-sectional, patient self-reported global e-survey conducted from February to June 2022. Data on demographics, SSc/SAID disease characteristics, COVID-19 infection history, and vaccination details including delayed ADEs as defined by the Centre for Disease Control were captured and analysed. Among 17,612 respondents, 10,041 participants fully vaccinated against COVID-19 were included for analysis. Of these, 2.6% (n = 258) had SSc, 63.7% other SAIDs, and 33.7% were HCs. BNT162b2 Pfizer (69.4%) was the most administered vaccine, followed by MRNA-1273 Moderna (32.25%) and ChadOx1 nCOV-19 Oxford/AstraZeneca (12.4%) vaccines. Among patients with SSc, 18.9% reported minor, while 8.5% experienced major delayed ADEs, and 4.6% reported hospitalization. These frequencies were comparable to those of the ADEs reported by other patients with SAIDs and HCs. However, patients with SSc reported a higher frequency of difficulty in breathing than HCs [OR 2.3 (1.0-5.1), p = 0.042]. Patients with diffuse cutaneous SSc experienced minor ADEs [OR 2.1 (1.1-4.4), p = 0.036] and specifically fatigue more frequently [OR 3.9 (1.3-11.7), p = 0.015] than those with limited cutaneous SSc. Systemic sclerosis patients with concomitant myositis reported myalgia more frequently [OR 3.4 (1.1-10.7), p = 0.035], while those with thyroid disorders were more prone to report a higher frequency of joint pain [OR 5.5 (1.5-20.2), p = 0.009] and dizziness [OR 5.9 (1.3-27.6), p = 0.024] than patients with SSc alone. A diagnosis of SSc did not confer a higher risk of delayed post-COVID-19 vaccine-related ADEs overall compared with other SAIDs and HCs. However, the diffuse cutaneous phenotype and coexisting autoimmune conditions including myositis and thyroid disease may increase the risk of minor ADEs. These patients may benefit from pre-vaccination counselling, close monitoring, and early initiation of appropriate care in the post-COVID-19 vaccination period.

Thrombosis with thrombocytopenia syndrome (TTS) following adenovirus vector COVID-19 vaccination in Canada

INTRODUCTION

Identifying and monitoring adverse events following vaccination contributed to the safety and effectiveness of COVID-19 mass vaccination campaigns. In March 2021, international reports emerged of an adverse event following vaccination with adenovirus vector COVID-19 vaccines (ChAdOx1-S [recombinant] and Ad26.COV2.S) of thrombosis with low platelet counts, referred to as thrombosis with thrombocytopenia syndrome (TTS). We described TTS reports in Canada following adenovirus vector COVID-19 vaccines and investigated whether the observed number of events were higher than expected.

METHODS

Reports of TTS following receipt of ChAdOx1-S [recombinant] or Ad26.COV2.S meeting the Canadian case definition for TTS and diagnostic certainty levels 1-3 of the Brighton Collaboration case definition, submitted to the Canadian Adverse Events Following Immunization Surveillance System and Canada Vigilance Database between February 26, 2021 and October 31, 2022 were included. Demographics and characteristics of the TTS reports are described along with an analysis comparing the observed number of reports to the expected number.

RESULTS

As of October 31, 2022, 56 reports of TTS following administration of ChAdOx1-S [recombinant] and no reports following Ad26.COV2.S vaccines were reported in Canada, of which 37 had functionally positive anti-PF4 antibodies. The median age was 56 years; males accounted for 54 % of reports. Five deaths were reported. The observed number of reports exceeded the expected for all ages and sexes combined, as well as for males aged 30-49 and 60-69 years, and females aged 40-59 years.

CONCLUSION

Based on international surveillance data, Canada evaluated a statistical signal of TTS following adenovirus vector vaccines. The investigation of this signal demonstrated how post-market vaccine safety surveillance systems were successful in investigating rare adverse events during the rollout of COVID-19 vaccines in Canada. As adenovirus vector vaccines continue to be administered, characterization of the association between the vaccine and TTS informs immunization programs and policies.

Evaluation of vaccination status of children with special health care needs in Suzhou, China, 2020-2022: A retrospective survey study

Children with special health care needs (CSHCNs) are at an increased risk of vaccine-preventable infections (VPDs), but they also face the dilemma of vaccine hesitancy. We obtained information on pediatric visits from the Referral and Assessment Information System for Vaccination (RAISV) and information on vaccination from the Jiangsu Province Immunization Information System (JSIIS). We followed the occurrence of Adverse Events Following Immunization (AEFIs) and VPDs by actively calling and querying the China Information System for Disease Control and Prevention (CISDCP). The Poisson test was used to compare the incidence of AEFIs between groups. A total of 5,037 children who visited a vaccination assessment clinic were followed-up in this study. The majority were children with developmental anomalies (28.5%), certain conditions originating in the perinatal period (12.1%), and nervous system disorders (9.0%). Most CSHCNs (66.9%) were advised to have all vaccines according to routine practice, 29.0% were advised to have partial vaccination, and 4.1% were advised to delay all vaccines and wait for future assessment. A total of 201 (4.0%) CSHCNs were not vaccinated, although they were assessed to be eligible for vaccination. By querying the immunization planning module in CISDCP, we observed 55 AEFI cases, which amounted to an incidence rate of 1.2 per 1,000, and the occurrence of abnormal reactions was not significantly different compared with the general population. The vaccination program following the designed workflow for CSHCNs was safe and could be recommended in other areas.

Spontaneously reported adverse events following COVID-19 basic and booster immunizations in the Netherlands

INTRODUCTION

The rapid roll-out of novel COVID-19 vaccines made near real-time post-marketing safety surveillance essential to identify rare and long-term adverse events following immunization (AEFIs). In light of the ongoing booster vaccination campaigns, it is key to monitor changes in observed safety patterns post-vaccination. The effect of sequential COVID-19 vaccinations, as well as heterologous vaccination sequences, on the observed post-vaccination safety pattern, remains largely unknown.

METHODS

The primary objective of this study was to describe the profile of spontaneously reported AEFIs following COVID-19 vaccination in the Netherlands, including the primary and booster series. Reports from consumers and healthcare professionals were collected via a COVID-19 vaccine-tailored online reporting form by the National Pharmacovigilance Centre Lareb (Lareb) between 6 January 2021 and 31 August 2022. The data were used to describe the most frequently reported AEFIs per vaccination moment, the consumer experienced burden per AEFI, and differences in AEFIs reported for homologous and heterologous vaccination sequences.

RESULTS

Lareb received 227,884 spontaneous reports over a period of twenty months. Overall, a high degree of similarity in local and systemic AEFIs per vaccination moment was observed, with no apparent change in the number of reports of serious adverse events after multiple COVID-19 vaccinations. No differences in the pattern of reported AEFIs per vaccination sequence was observed.

CONCLUSION

Spontaneous reported AEFIs demonstrated a similar reporting pattern for homologous and heterologous primary and booster series of COVID-19 vaccination in the Netherlands.

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.

Serious adverse event following immunization and thromboembolic events associated with COVID19 vaccination: An analysis of nationwide causality assessment from India

BACKGROUND

Vaccines against the COVID-19 pandemic were introduced in late 2020. The present study has been conducted to study the serious Adverse Events Following Immunization (AEFIs) reported for COVID-19 vaccines from India.

METHODS

Secondary data analysis of the causality assessment reports for the 1112 serious AEFIs published by the Ministry of Health & Family Welfare, Government of India, was conducted. For the current analysis, all the reports published till 29.03.2022 were included. The primary outcome variables analyzed were the consistent causal association and the thromboembolic events.

RESULTS

The majority of the serious AEFIs assessed were either coincidental (578, 52%) or vaccine product related (218, 19.6%). All the serious AEFIs were reported among the Covishield (992, 89.2%) and COVAXIN (120, 10.8%) vaccines. Among these, 401 (36.1%) were deaths, and 711 (63.9%) were hospitalized and recovered. On adjusted analysis, females, the younger age group and non-fatal AEFIs showed a statistically significant consistent causal association with COVID-19 vaccination. Thromboembolic events were reported among 209 (18.8%) of the analyzed participants, with a significant association with higher age and case fatality rate.

CONCLUSION

Deaths reported under serious AEFIs were found to have a relatively lower consistent causal relationship with the COVID-19 vaccines than the recovered hospitalizations in India. No consistent causal association was found between the thromboembolic events and the type of COVID-19 vaccine administered in India.

Adverse events following immunization associated with coronavirus disease 2019 (COVID-19) vaccines: A descriptive analysis from VigiAccess

This study assessed adverse events following immunizations (AEFIs) reported on COVID-19 vaccines in VigiAccess and determined the reporting trends across all continents of the world. The study was cross-sectional quantitative in design. VigiAccess was searched on 10 November 10 2021 for reported adverse events following the introduction of COVID-19 vaccines. After entering the search term, "COVID-19 vaccines" in VigiAccess, AEFIs associated with nine approved brands of COVID-19 vaccines had been documented in the database. Data were captured among age groups, sex, and continents of the world and analyzed using Statistical Package for Social Sciences (SPSS) version 25. Overall, 2,457,386 AEFIs had been reported in VigiAccess at the time of the search. No causal associations could be established between the vaccines and the AEFIs. The public accessing VigiAccess data should therefore be made aware of this in order to not falsely attribute AEFIs to COVID-19 vaccines when assessing the database.

Barriers to healthcare workers reporting adverse events following immunization in Zhejiang province, China

Objectives

A cross-sectional survey was conducted among healthcare workers (HCWs) to assess their knowledge, attitude, and reporting behavior in adverse event following immunization (AEFI) surveillance as well as to identify barriers.

Methods

A simple random sample of 170 vaccination clinics was selected and one HCW was informed to participate in this survey in each selected vaccination clinic. The survey was developed using a secure online platform and consisted of a structured online questionnaire. The distributions of the respondents’ characteristics were presented. Training status, knowledge, attitude, and reporting behavior were compared between sub-groups of HCWs. Barriers and suggestions on AEFI reporting were also summarized.

Results

Of the 170 surveyed HCWs, 61.76% received the training on AEFI surveillance while 15.88% had no AEFI training at all. The higher level of knowledge and the more positive attitude and reporting behavior on AEFI surveillance were observed among HCWs with the longer working duration on AEFI surveillance, or among HCWs who received the training. The most critical barrier to reporting an AEFI was ‘not being sure if the AEFI is related to the vaccine’ (122, 71.76%). Other barriers were: ‘I do not want to raise unnecessary public alarm about a vaccine’ (105, 61.76%); ‘reporting form or other method being too complicated’ (65, 38.23%).

Conclusion

The study findings highlighted the need to prioritize training on AEFI surveillance for HCWs. It is recommended that the development of the targeted interventions to strengthen AEFI surveillance system be required based on the barriers found in this study.

Enhanced surveillance for adverse events following immunization during the 2019 typhoid conjugate vaccine campaign in Harare, Zimbabwe

BACKGROUND

During February 25-March 4, 2019, Zimbabwe's Ministry of Health and Child Care conducted an emergency campaign using 342,000 doses of typhoid conjugate vaccine (TCV) targeting individuals 6 months-15 years of age in eight high-risk suburbs of Harare and up to 45 years of age in one suburb of Harare. The campaign represented the first use of TCV in Africa outside of clinical trials.

METHODS

Three methods were used to capture adverse events during the campaign and for 42 days following the last dose administered: (1) active surveillance in two Harare hospitals, (2) national passive surveillance, and (3) a post-campaign coverage survey.

RESULTS

Thirty-nine adverse events were identified during active surveillance, including 19 seizure cases (16 were febrile), 16 hypersensitivity cases, 1 thrombocytopenia case, 1 anaphylaxis case, and two cases with two conditions. Only 21 (54%) of 39 patients were hospitalized and 38 recovered without sequelae. Attack rates per 100,000 TCV doses administered were highest for seizures (6.27) and hypersensitivity (5.02). Only 6 adverse events were reported through passive surveillance by facilities other than the two active surveillance hospitals. A total of 177 (10%) of 1,817 vaccinees surveyed reported experiencing an adverse event during the post-campaign coverage survey, of which 25 (14%) sought care.

CONCLUSIONS

In line with previous evaluations of TCV, enhanced adverse event monitoring during an emergency campaign supports the safety of TCV. The majority of reported events were minor or resulted in recovery without long-term sequelae. Attack rates for seizures and hypersensitivity were low compared with previous active surveillance studies conducted in Kenya and Burkina Faso. Strengthening adverse event monitoring in Zimbabwe and establishing background rates of conditions of interest in the general population may improve future safety monitoring during new vaccine introductions.

Myocarditis and/or pericarditis risk after mRNA COVID-19 vaccination: A Canadian head to head comparison of BNT162b2 and mRNA-1273 vaccines

Background

Canadian and international data suggest the risk of myocarditis and/or pericarditis is elevated during the week after mRNA COVID-19 vaccination, particularly in younger age groups, in males, and after second doses.

Objectives

This article examines whether there is a product-specific difference in the risk for myocarditis and/or pericarditis between the two mRNA vaccines administered in Canada: BNT162b2 (Pfizer-BioNTech Comirnaty) and mRNA-1273 (Moderna Spikevax).

Materials and methods

Reporting rates of myocarditis and/or pericarditis were calculated from reports received by the Canadian Adverse Events Following Immunization Surveillance System from December 2020-March 2022. Excess cases and attributable incidence among individuals aged 18–39 were estimated for each vaccine in comparison with background rates from 2015 to 2019. Head-to-head comparisons used Poisson regression, conditioned on week of vaccine administration, to estimate rate ratios for the week after mRNA-1273 vaccination versus the week after BNT162b2, by age and sex as well as overall. Analyses were restricted to May 30–March 13, 2021, when heightened media awareness was unlikely to have affected reporting rates for the two products differentially.

Results

In 18–29 year-old males who received a second dose of mRNA COVID-19 vaccine, attributable risk of myocarditis and/or pericarditis was found to be 5.69 (95% CI: 4.07 – 7.95; p < 0.001) times higher among mRNA-1273 recipients (n = 106) as compared to BNT162b2 recipients (n = 33). In the same group, Poisson regression modelling estimated that the risk of myocarditis and/or pericarditis was 4.72 (p-value = <0.001) times higher after mRNA-1723 compared to BNT162b2 vaccination.

Conclusions

The risk of myocarditis and/or pericarditis is higher after mRNA-1723 vaccination than BNT162b2 vaccination in those aged 18–39 years, especially in males aged 18–29 years, where the risk is several times higher.

Analyzing the U.S. Post-marketing safety surveillance of COVID-19 vaccines

INTRODUCTION

Since December 2020, three COVID-19 vaccines have been authorized in the United States (U.S.) and were proceeded by large immunization programs. The aim of this study was to characterize the U.S. post-marketing safety (PMS) profiles of these vaccines with an in-depth analysis of mortality data.

METHODS

This was a retrospective database analysis study. Details of the U.S. PMS reports (15 December 2020 to 19 March 2021) of the three vaccines (Pfizer-BioNTech, Moderna, and Janssen Ad26.COV2.S) were retrieved from the U.S. Vaccine Adverse Event Reporting System (VAERS). A descriptive analysis was conducted to characterize the reported adverse events (AEs). A comparative (Pfizer-BioNTech vs. Moderna) analysis of mortality was conducted. The mean count ratio of death between the two vaccines was estimated using a negative binomial regression model adjusting for the measured confounders.

RESULTS

A total of 44,451 AE reports were retrieved (corresponding to 0.05% of the U.S. population who received at least one dose). The most commonly reported AEs were injection site reactions (30.4% of the reports), pain (reported in 26.7% of the reports), and headache (18.6% of the reports). Serious AEs were reported in only 14.6% of the reports with 4,108 hospitalizations. The total number of deaths was 1,919 with a mean count ratio of Moderna (n = 997) vs. Pfizer-BioNTech (n = 899) of 1.07 (95% confidence interval 0.86 to 1.33).

CONCLUSIONS

The vast majority of PMS AEs in the U.S. were non-serious, and the number of serious AEs is very low given the total number of vaccinated U.S. population.

Analysis of the adverse events following immunization with inactivated quadrivalent influenza vaccine from 2018 to 2020 in Zhejiang province, with a comparison to trivalent influenza vaccine

OBJECTIVES

To summarize reports to the national adverse event following immunization surveillance system (NAEFISS) following inactivated quadrivalent influenza vaccine (QIV) in Zhejiang province from 2018 to 2020.

METHODS

We analyzed adverse events following immunization (AEFI) reports following QIV, with a comparison, with the AEFI reports following inactivated trivalent influenza vaccine (TIV). Reporting rates of AEFI were calculated by age, severity of AEFI, categories of AEFI, and reaction categories. The data mining algorithm used in this study was reporting odds ratio (ROR). A value of ROR‑1.96SE >1 (standard error [SE]) was considered as positive signal. These reporting rates between vaccine types were compared through chi-square tests.

RESULTS

NAEFISS received 514 AEFI reports following QIV and 536 reports following TIV, with a reporting rate of 13.66/100,000 100,000 doses/100,000 doses (χ² = 7.11, P> .05). Of the 514 reports following QIV, 410 were vaccine product-related reactions and 51 were severe AEFI. Fever/redness/induration was the most frequent clinical diagnosis of the QIV AEFI, with a reporting rate of 12.42/100,000 doses in the age group of 3-17 years, and 12.44/100,000 doses in the age group of ≥18 years. The positive signal of QIV AEFI was observed for the allergic rash and asthma/wheezing.

CONCLUSION

The present analysis did not identify any new/unexpected safety concerns. We suggested that NAEFISS continue to monitor the safety of QIV.

Disproportionality analysis of reported drug adverse events to assess a potential safety signal for pentavalent vaccine in 2019 in El Salvador

Detection and surveillance of vaccine safety hazards is a public health staple. In the post-marketing phase, when vaccines are used in mass, it is crucial to monitor potential signals of adverse reactions that may have been missed in the pre-marketing phase. We analysed spontaneous reports of drug adverse events in El Salvador to assess a potential safety signal related to an increase in febrile seizures following the pentavalent (diphtheria, tetanus, pertussis, hepatitis B, and Haemophilus influenzae Type B) vaccine in 2019. This was a retrospective observational study of adverse event notifications in the national electronic drug safety database from 2011 to 2019. We performed standard disproportionality analysis computing Proportional Reporting Risk (PRR), Reporting Odds Ratio (ROR), Relative Reporting Ratio (RRR), Chi-squared, and Information Component (IC), comparing the pairing of febrile seizures and pentavalent vaccine to all other drugs and adverse events recorded in 2019. The occurrence of febrile seizures following pentavalent vaccination exceeded the WHO expected rate of six cases × 100 000 doses administered from April 2019, with a maximum of 9.2 in September. IC was 4.3, ORR 421.9 (95% Confidence Interval, CI: 123.8-1437.7), PRR 223.5 (95 %CI: 70.2-710.9), RRR was 19.5. The first booster presented the highest rate (14.6 per 100,000 doses) of febrile seizures, more than double than expected. Rates for 2018 remained below expected. Reports of febrile seizures following pentavalent vaccine were also on the increase globally since 2014, with highest rates in 2018 and 2019. There was a disproportion of febrile seizures notifications following pentavalent in El Salvador in 2019, suggesting the existence of a safety signal. This may be due to the change in provider. Further studies should assess the causes of the increase and compute costs and benefits of this vaccination to determine if switching to a less reactogenic vaccine formulation is indicated.

The characteristics and trend of adverse events following immunization reported by information system in Jiangsu province, China, 2015-2018

OBJECTIVE

Adverse events following immunization is an important factor influencing public trust in vaccination. Publicizing its incidence timely can increase public trust. The aim of this study is to describe the incidence and characteristics of adverse events following immunization in Jiangsu province of China from 2015 to 2018.

METHODS

All information of adverse events following immunization (AEFIs) was gained from Jiangsu Province Vaccination Integrated Service Management Information System. The reported AEFI trend was analyzed using Chi-square test.

RESULTS

A total of 77,980 AEFI cases were reported through the AEFI system; Among which, 77,731 were classified as non-serious AEFI cases and 249 were serious AEFI cases. The male to female ratio was 1.31:1, cases less than 7 years old accounted for 97.7%. The total estimated AEFI rate was 62.70/100,000 doses. By severity, 60.75/100,000, 4.46/100,000 and 0.11/100,000 AEFI cases were common vaccine reaction, rare vaccine reaction, and serious rare vaccine reaction, respectively. The top two serious AEFI were thrombocytopenic purpura and febrile. The incidence rates showed the increasing trend and the linear trend of the increasing incidence rates passed the significant test at 0.05 levels.

CONCLUSION

The sensitivity of AEFI monitoring in Jiangsu Province is increasing and higher than the national average and most countries. The majority of AEFI cases were common adverse reactions, while the serious vaccine reactions caused by vaccines were extremely low. To elevate the sensitivity of AEFI surveillance may reduce the incidence of developing serious AEFI cases.

Safety of SARS-CoV-2 vaccines: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Various modalities of vaccines against coronavirus disease 2019 (COVID-19), based on different platforms and immunization procedures, have been successively approved for marketing worldwide. A comprehensive review for clinical trials assessing the safety of COVID-19 vaccines is urgently needed to make an accurate judgment for mass vaccination.

MAIN TEXT

A systematic review and meta-analysis was conducted to determine the safety of COVID-19 vaccine candidates in randomized controlled trials (RCTs). Data search was performed in PubMed, Embase, Cochrane library, Scopus, Web of Science, and MedRxiv. Included articles were limited to RCTs on COVID-19 vaccines. A total of 73,633 subjects from 14 articles were included to compare the risks of adverse events following immunization (AEFI) after vaccinating different COVID-19 vaccines. Pooled risk ratios (RR) of total AEFI for inactivated vaccine, viral-vectored vaccine, and mRNA vaccine were 1.34 [95% confidence interval (CI) 1.11-1.61, P < 0.001], 1.65 (95% CI 1.31-2.07, P < 0.001), and 2.01 (95% CI 1.78-2.26, P < 0.001), respectively. No significant differences on local and systemic AEFI were found between the first dose and second dose. In addition, people aged ≤ 55 years were at significantly higher risk of AEFI than people aged ≥ 56 years, with a pooled RR of 1.25 (95% CI 1.15-1.35, P < 0.001).

CONCLUSIONS

The safety and tolerance of current COVID-19 vaccine candidates are acceptable for mass vaccination, with inactivated COVID-19 vaccines candidates having the lowest reported AEFI. Long-term surveillance of vaccine safety is required, especially among elderly people with underlying medical conditions.

Safety of SARS-CoV-2 vaccines: a systematic review and meta-analysis of randomized controlled trials

Background

Various modalities of vaccines against coronavirus disease 2019 (COVID-19), based on different platforms and immunization procedures, have been successively approved for marketing worldwide. A comprehensive review for clinical trials assessing the safety of COVID-19 vaccines is urgently needed to make an accurate judgment for mass vaccination.

Main text

A systematic review and meta-analysis was conducted to determine the safety of COVID-19 vaccine candidates in randomized controlled trials (RCTs). Data search was performed in PubMed, Embase, Cochrane library, Scopus, Web of Science, and MedRxiv. Included articles were limited to RCTs on COVID-19 vaccines. A total of 73,633 subjects from 14 articles were included to compare the risks of adverse events following immunization (AEFI) after vaccinating different COVID-19 vaccines. Pooled risk ratios (RR) of total AEFI for inactivated vaccine, viral-vectored vaccine, and mRNA vaccine were 1.34 [95% confidence interval (CI) 1.11–1.61, P < 0.001], 1.65 (95% CI 1.31–2.07, P < 0.001), and 2.01 (95% CI 1.78–2.26, P < 0.001), respectively. No significant differences on local and systemic AEFI were found between the first dose and second dose. In addition, people aged ≤ 55 years were at significantly higher risk of AEFI than people aged ≥ 56 years, with a pooled RR of 1.25 (95% CI 1.15–1.35, P < 0.001).

Conclusions

The safety and tolerance of current COVID-19 vaccine candidates are acceptable for mass vaccination, with inactivated COVID-19 vaccines candidates having the lowest reported AEFI. Long-term surveillance of vaccine safety is required, especially among elderly people with underlying medical conditions.

Graphic Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s40249-021-00878-5.

Revaccination outcomes of children with vaccine proximate seizures

BACKGROUND

Seizures, whether febrile or afebrile, occurring within 14 days following vaccination can be considered as vaccine proximate seizures (VPSs). While the attributable risk and clinical severity of first febrile VPS is well known, the risk and clinical outcomes of VPS recurrence is less well defined.

METHODS

We conducted a retrospective review of revaccination management and outcomes in children who experienced a VPS as their first seizure seen in Australian Specialist Immunisation Clinics between 2013 and 2017. Vaccination outcomes were compared between children who had a VPS as their only seizure (VPS only) and children who had further non-vaccine proximate seizures following their initial VPS (VPS+) prior to review at the clinic.

RESULTS

We identified 119 children with a VPS as their first seizure, of which 61 (51%) went on to have other seizures (VPS+). Children with VPS+ were more likely to present at a younger age (6.2 vs 12.5 months, P = 0.03), with afebrile seizures (42.6% vs 15.5%, P = 0.002) compared to VPS only children. VPS recurrence on revaccination was uncommon in both groups, but more common in VPS+ children (12.5% vs 2.4%, P = 0.07). Having an epilepsy diagnosis, specifically Dravet syndrome, was associated with VPS recurrence (P < 0.001). Of the four children with Dravet syndrome who had VPS recurrence, all had status epilepticus following revaccination.

CONCLUSION

In children who presented with a single VPS as their only seizure, VPS recurrence on revaccination was uncommon. Children who had multiple non-vaccine proximate seizures following their initial VPS (VPS+) were more likely to present with afebrile VPS, at a younger age and have a VPS recurrence with vaccination. In these children, particularly those aged < 12 months, assessment and investigation for diagnosis of Dravet syndrome should be considered and additional precautions for revaccination undertaken as they are at highest risk of VPS recurrence.

Post-marketing safety surveillance for inactivated Enterovirus 71 vaccines in Jiangsu, China from 2017 to 2019

INTRODUCTION

Two types of enterovirus 71 (EV71) vaccines, manufactured using human diploid (H2) and Vero cells, have been administered in Jiangsu Province, China since 2017. In this study, we evaluated their safety profiles using records collected from the Chinese National Adverse Events Following Immunization (AEFIs) Information System (CNAEFIS) and Electronic Immunization Registries System (EIRS) between 2017 and 2019.

METHODS

Demographic characteristics of the patients, AEFI incidence rates(IRs), symptoms, and time intervals were summarized from the reported AEFI data in the CNAEFIS. Also, the administered doses of the two vaccines were exported from the EIRS to calculate the IRs of AEFIs and thus compare the AEFIs between the two types of EV71 vaccines.

RESULTS

In total, 209, 407, and 344 AEFIs cases following EV71 vaccine administration were reported during 2017, 2018, and 2019, respectively, yielding IRs of 59.2, 48.2, and 54.2 per 100,000 doses, respectively. Fever, irritability, allergic eruptions, fatigue, loss of appetite, redness and induration at the injection site were the most commonly reported AEFIs. No significant differences in rare reactions were found between the two types of EV71 vaccinations. The majority of AEFIs were developed within 30 min to 3 days after administration.

CONCLUSION

EV71 vaccines showed satisfactory safety profiles since their first use 3 years ago in the Jiangsu Province. The AEFI profiles were identical to those in pre-marketing studies; most AEFIs after vaccination were mild and common. More active surveillance studies should be performed to provide more comprehensive post-marketing safety data.

Lessons on causality assessment and communications from the 2019 South-East Asia Regional (SEAR) workshop on inter-country expert review of selected Adverse Events Following Immunization (AEFI) cases

BACKGROUND

Surveillance of AEFI is fundamental for improving safety and maintaining public support for vaccination. In SEAR, billions of doses of vaccine are given annually. The objective of the 2019 SEAR AEFI training workshop was to further strengthen in-country vaccine safety, assess capacity compared to 2014 and to better integrate communication into the AEFI causality assessment program.

METHODS

A 3 ½ day workshop with AEFI experts from all 11 SEAR countries. Participants outlined each county's AEFI data, critiqued their AEFI program, reviewed and critiqued causality assessment of 23 anonymized serious AEFI cases and proposed communication plans for each.

RESULTS

Between 2016 and 2018, over 2.9 billion doses of vaccine were given in SEAR. Compared to 2014, AEFI detection and causality assessment skills had improved. AEFI experts' communication planning skills markedly improved during the workshop. Good concordance was found between country causality assessment findings and the workshop critiques. A list of targeted recommendations (country, regional and global levels) arose from the workshop.

CONCLUSIONS

SEAR countries have much improved their AEFI detection and causality assessment expertise since 2014. Given the high volume of doses administered and the AEFI technical expertise, SEAR countries can well monitor safety of regionally produced vaccines. Integration of AEFI communication into AEFI causality assessment can help mitigate potential negative impacts of serious AEFIs.

Causality assessment of adverse events following immunization: the problem of multifactorial pathology

The analysis of Adverse Events Following Immunization (AEFI) is important in a balanced epidemiological evaluation of vaccines and in the issues related to national vaccine injury compensation programs. If manufacturing defects or vaccine storage and delivering errors are excluded, the majority of adverse reactions to vaccines occur as excessive or biased inflammatory and immune responses. These unwanted phenomena, occasionally severe, are associated with many different endogenous and exogenous factors, which often interact in complex ways. The confirmation or denial of the causal link between an AEFI and vaccination is determined pursuant to WHO guidelines, which propose a four-step analysis and algorithmic diagramming. The evaluation process from the onset considers all possible "other causes" that can explain the AEFI and thus exclude the role of the vaccine. Subsequently, even if there was biological plausibility and temporal compatibility for a causal association between the vaccine and the AEFI, the guidelines ask to look for any possible evidence that the vaccine could not have caused that event. Such an algorithmic method presents some concerns that are discussed here, in the light of the multifactorial nature of the inflammatory and immune pathologies induced by vaccines, including emerging knowledge of genetic susceptibility to adverse effects. It is proposed that the causality assessment could exclude a consistent association of the adverse event with the vaccine only when the presumed "other cause" is independent of an interaction with the vaccine. Furthermore, the scientific literature should be viewed not as an exclusion criterion but as a comprehensive analysis of all the evidence for or against the role of the vaccine in causing an adverse reaction. These issues are discussed in relation to the laws that, in some countries, regulate the mandatory vaccinations and the compensation for those who have suffered serious adverse effects.

Causality assessment of adverse events following immunization: the problem of multifactorial pathology

The analysis of Adverse Events Following Immunization (AEFI) is important in a balanced epidemiological evaluation of vaccines and in the issues related to vaccine injury compensation programs. The majority of adverse reactions to vaccines occur as excessive or biased inflammatory and immune responses. These unwanted phenomena, occasionally severe, are associated with many different endogenous and exogenous factors, which often interact in complex ways. The confirmation or denial of the causal link between an AEFI and vaccination is determined pursuant to WHO guidelines, which propose a four-step analysis and algorithmic diagramming. The evaluation process from the onset considers all possible "other causes" that might explain the AEFI and thus exclude the role of the vaccine. Subsequently, even if there was biological plausibility and temporal compatibility for a causal association between the vaccine and the AEFI, the guidelines ask to look for any possible evidence that the vaccine could not have caused that event. Such an algorithmic method presents several concerns that are discussed here, in the light of the multifactorial nature of the inflammatory and immune pathologies induced by vaccines, including emerging knowledge of genetic susceptibility to adverse effects. It is proposed that the causality assessment could exclude a consistent association of the adverse event with the vaccine only when the presumed "other cause" is independent of an interaction with the vaccine. Furthermore, the scientific literature should be viewed not as an exclusion criterion but as a comprehensive analysis of all the evidence for or against the role of the vaccine in causing an adverse reaction. Given these inadequacies in the evaluation of multifactorial diseases, the WHO guidelines need to be reevaluated and revised. These issues are discussed in relation to the laws that, in some countries, regulate the mandatory vaccinations and the compensation for those who have suffered serious adverse effects.

[Study on surveillance data of adverse events following immunization of seasonal influenza vaccine in China during 2015-2018 influenza season]

Objective: To analyze the occurrence features of adverse events following immunization (AEFI) of Seasonal Influenza Vaccines (InfV) used in China, 2015-2018 influenza season. Methods: InfV (including concurrent administered with other vaccines) AEFI data were collected through the Chinese national AEFI information system during 2015.9.1-2018.8.31 (excluding Chinese Hong Kong, Macao and Taiwan data). The vaccine lot release data were collected from National Institutes for Food and Drug Control published database. Time periods of three influenza season were 2015.9.1-2016.8.31, 2016.9.1-2017.8.31, 2017.9.1-2018.8.31. The vaccines used and included in this analysis were trivalent inactivated influenza vaccine (IIV3)-Split, IIV3-Split (Children) and IIV-subnit. The incidence of AEFI were calculated (per 100 000 release doses), and epidemiological characteristic were analyzed using descriptive methodology. Results: A total of 8 464 InfV AEFIs were collected in 2015-2018 influenza season from National AEFI Information System, in which 5 646 were IIV3-split, with the rate of 10.64/100 000 release doses, 2 818 were IIV3-split (Children), with the rate of 9.355/100 000 release doses. The most common symptom was fever (axillary temperature ≥37.1 ℃) within vaccine reactions, with a number of 6 207 cases. In which, there were 3 554 cases with fever (axillary temperature ≥38.6 ℃) and the estimated reporting rate was 4.274/100 000 release doses. In all rare vaccine reactions, the most common diagnosis was anaphylactic rash(442, 0.531/100 000 release doses) and angioedema (70, 0.084/100 000 release doses). Even the rates of serious rare vaccine reactions were low, febrile Convulsion (27, 0.032/100 000 release doses) and Henoch-Schönlein Purpura(HSP) (21, 0.025/100 000 release doses) were relatively common in serious rare vaccine reactions during the study period. Conclusion: The estimated rate of rare vaccine reactions related toInfV was relatively low. In all vaccine reactions, fever was the most common symptoms. The most common diagnosis of non-serious rare vaccine reaction were anaphylactic rash and angioedema. The incidence of serious rare vaccine reactions was low.

Deaths reported to national surveillance for adverse events following immunization in China, 2010-2015

BACKGROUND

The national Adverse Events Following Immunization (AEFI) surveillance system in China (CNAEFIS) has collected AEFI reports -including deaths following all vaccines used in China since 2008.

AIMS

To review reports of AEFI-associated death cases from 2010 to 2015 to assess potential vaccine safety issues.

METHODS

Descriptive analysis of epidemiologic characteristic of AEFI-associated death cases and standard causality assessment for reported causes of deaths. To estimate the risk of death after vaccination, we used population data, administered doses and live births to calculate denominators.

RESULTS

During 2010-2015, 753 deaths were reported to CNAEFIS from mainland China. Highest numbers were reported in 2013 and 2014 when reporting peak of AEFI-associated deaths occurred after media reports concerning "death following Hepatitis B vaccination" in China. About 95% of deaths were in children <5 years of age and males accounted for 60%. Most common vaccines associated with reports of fatal AEFIs were vaccines in national immunization schedule. In causality assessment, 120 (16.0%) deaths were classified as vaccine-associated reactions such as anaphylactic reactions and disseminated BCG infections; 594 (78.9%) deaths were identified as coincidental events. The main causes of death were asphyxia, and Sudden Infant Death Syndrome. The overall estimated AEFI-associated death rates were: 0.26 per million vaccination doses administered and 0.09 per million population. The neonatal AEFI death rate was 0.77 per million live births.

CONCLUSIONS

These data provide reassuring information about the small risk of death following immunization. They also illustrate sensitivity of passive reporting to public information and that peaks in serious AEFI reports should be interpreted with caution. Continuous monitoring and scientific causality assessment for serious AEFIs, including AEFI-associated deaths is imperative to ensure public confidence in the immunization program.

The association of adverse events with bivalent human papilloma virus vaccination: A nationwide register-based cohort study in Finland

BACKGROUND

A bivalent HPV vaccine (Cervarix®; HPV2, GlaxoSmithKline) was introduced into the Finnish national vaccination programme (NVP) in November 2013 for girls aged 11-13 years with a catch-up for 14-15 year-olds. We evaluated the association between HPV2 and selected autoimmune diseases and clinical syndromes by conducting a nation-wide retrospective register-based cohort study.

METHODS

First life-time occurrences of the relevant ICD-10 codes in girls aged 11-15 years between Nov-2013 and Dec-2016 were obtained from the national hospital discharge register. Population denominators were obtained from the Population Information System and vaccination records from the National Vaccination Register. Registers were linked using unique personal identity codes. Association between HPV2 and 38 selected outcomes were studied using Cox regression, with age as the main time-scale and the first vaccination dose as the time-dependent exposure. The hazard ratios (HR) with 95%CI were assessed according to the time since exposure (entire follow-up, 0-180/181-365/>365 days).

RESULTS

Of 240 605 girls eligible for HPV2 vaccination, 134 615 (56%) were vaccinated. After adjustment for geographical area (6 hospital districts), country of origin (Finnish-born/not) and number of hospital contacts from 9 through 10 years of age, HRs ranged from 0.34 (95%CI 0.11-1.05) to 8.37 (95%CI 0.85-82.54) and HPV2 vaccination was not statistically significantly associated with a higher risk of any outcome during the entire follow-up.

CONCLUSIONS

This study found no significantly increased risk for the selected outcomes after the HPV vaccination in girls 11-15 years of age. These results provide valid evidence to counterbalance public scepticism, fears of adverse events and possible opposition to HPV vaccination and consequently can contribute to increase HPV vaccination coverage in Finland as well as elsewhere.

Causality assessment of serious and severe adverse events following immunization in India: a 4-year practical experience

BACKGROUND

India has implemented the World Health Organization's revised Causality Assessment Protocol for adverse events following immunization (AEFI). We describe the number and types of serious/severe AEFIs, including deaths.

RESEARCH DESIGN AND METHODS

Analysis of causality classification of reported serious/severe AEFIs from 1 January 2012 to 7 January 2016 was done. Classification includes (A) consistent with causal association to immunization; (B) indeterminate; (C) coincidental association; or (D) unclassifiable. We present descriptive statistics across each category.

RESULTS

Analysis of causality assessment completed for 1037 reports of serious AEFIs: 499 (48%) were causally associated, 84 (8%) were indeterminate, 323 (31%) were coincidental, and 131 (13%) were unclassifiable. Of the 499 reports in the A category, the events were causally linked to vaccine product for 189 (18%), to immunization error for 135 (13%), and to immunization anxiety for 175 (17%). Among 279 reported deaths, more than half (55%; n = 153) were coincidental events and 37% were unclassifiable.

CONCLUSIONS

Causality assessment of AEFI cases is an important component of vaccination programs and post-marketing surveillance of vaccines. Field reporting and investigation of AEFIs can be improved for many severe or serious reports, most of which are not causally linked to the vaccination program.

Use of a new global indicator for vaccine safety surveillance and trends in adverse events following immunization reporting 2000-2015

Reporting of adverse events following immunization (AEFI) is a key component for functional vaccine safety monitoring system. The aim of our study is to document trends in the AEFI reporting ratio globally and across the six World Health Organization (WHO) regions. We describe the number of AEFI reports communicated each year through the World Health Organization/United Nations Children's Fund Joint Reporting Form on Immunization from 2000 to 2015. The AEFI reporting ratios (annual AEFI reports per 100,000 surviving infants) were calculated to identify WHO countries (n = 191 in 2000 and n = 194 by 2015) that met a minimal reporting ratio of 10, a target set by the Global Vaccine Action Plan for vaccine safety monitoring as a proxy measure for a functional AEFI reporting system. The number of countries reporting any AEFI fluctuated over time but with progress from 32 (17%) in 2000 to 124 (64%) in 2015. In 2015, the global average AEFI reporting ratio was 549 AEFI reports per 100,000 surviving infants. The number of countries with AEFI reporting ratios greater than 10 increased from 8 (4%) in 2000 to 81 (42%) in 2015. In 2015, 60% of countries in the WHO Region of the Americas reported at least 10 AEFI per 100,000 surviving infants, followed by 55% in European Region, 43% in Eastern Mediterranean Region, 33% in Western Pacific Region, 27% in South-East Asia Region and 21% in African Region. Overall, AEFI reporting has increased over the past sixteen years worldwide, but requires strengthening in a majority of low- and middle- income countries. The AEFI reporting ratio is useful for benchmarking and following trends over time; but does not provide information on the quality of the reporting system and does not guarantee capacity to detect and manage a vaccine safety problem at a national level. Additional efforts are required to ensure and improve data quality, AEFI reporting and surveillance of immunization safety in every country.

Evaluation of the adverse events following immunizations surveillance system in Harare City, Zimbabwe, 2016: a descriptive cross sectional study

Introduction

Vaccines safety are monitored by looking for Adverse Events Following Immunizations (AEFIs). A review of the 2014 Harare City consolidated monthly return form (T5) revealed that 28 AEFIs were seen in 2014. However, only 21 were reported through the system. We therefore evaluated the Harare City AEFI surveillance system to assess its usefulness.

Methods

A descriptive cross sectional study was conducted. Twenty one of 41 clinics were randomly selected and 51 health workers were randomly recruited. Interviewer administered questionnaires were used to collect data. Epi info 7 was used to generate frequencies, means and proportions.

Results

Out of 51 respondents, 50 (98%) knew the purpose of AEFI system, 48 (94%) knew at least two presenting symptoms of AEFIs and 39 (77%) knew the correct date of form submission to the next level. Receiving no feedback 24 (47.1%), fear of victimisation 16 (31.4%) and work overload 11 (21.6%) were the major reasons for under reporting. Eighty six percent perceived the system to be simple and 43 (84%) were willing to continue participating. Fifty three percent (27) reported taking public health actions (such as awareness campaigns & making follow ups) basing on AEFI data collected. All 46 reviewed forms were completely filled and submitted in time. All 21 clinics had written AEFI guidelines and case definitions. Only 14 of 21 clinics had adequately stocked emergency drugs. The total cost for a single notification was estimated at US$22.30.

Conclusion

The system was useful, simple, acceptable, timely, stable, representative but costly. The good performance of the system reported in this evaluation could be attributed to high health worker knowledge. Following this evaluation, replenishment of out of stock drugs and follow up of missing 2014 AEFI feedback from MCAZ were done. In addition, making the system electronic is recommended.

Post-marketing safety surveillance for inactivated and live-attenuated Japanese encephalitis vaccines in China, 2008-2013

INTRODUCTION

Two types of Japanese encephalitis (JE) vaccines, inactivated JE vaccine (JE-I) and live-attenuated JE vaccine (JE-L), are available and used in China. In particular, one JE-L, produced by a domestic manufacturer in China, was prequalified by WHO in 2013. We assessed the safety of JE vaccines in China during 2008-2013 using the Chinese National Adverse Events Following Immunization Information System (CNAEFIS) data.

METHODS

We retrieved AEFI reporting data about JE vaccines from CNAEFIS, 2008-2013, examined demographic characteristics of AEFI cases, and used administrative data on vaccine doses as denominator to calculate and compare crude reporting rates. We also used disproportionality reporting analysis between JE-I and JE-L to assess potential safety signals.

RESULTS

A total of 34,879 AEFIs related with JE-I and JE-L were reported, with a ratio of male to female as 1.3:1; 361 (1.0%) cases were classified as serious. JE vaccines were administered concurrently with one or more other vaccines in 13,592 (39.0%) of cases. The overall AEFI reporting rates were 214.4 per million vaccination doses for JE-L and 176.9 for JE-I (rate ratio [RR]: 1.2, 95% confidence interval [CI]: 1.1-1.3) in 2010-2013. Febrile convulsions (FC) following JE-I was found as a signal of disproportionate reporting (SDR). However, there was no significant difference between the reporting rates of FC of JE-I and JE-L (0.3 per million vaccination doses for JE-L, 0.4 for JE-I, p=0.05).

CONCLUSIONS

While our analysis did not find apparent safety concern of JE vaccines in China, further study should consider JE-I vaccines and febrile convulsion, and taking more sensitive methods to detect signals.

Dengue vaccine safety signal: Immune enhancement, waning immunity, or chance occurrence?

A new dengue vaccine was associated with increased risk of hospitalized virologically-confirmed disease during year 3 of follow-up among children age 2-5years. Among hypotheses to explain this finding, we could not distinguish definitively between antibody dependent enhancement, waning immunity, or chance occurrence. However, any theory must account for the following: (a) the signal occurred mainly because of decreased dengue among controls rather than increased dengue among vaccinees; (b) among 48 data points, a statistically significant increase in hospitalization among vaccinated children occurred for only one age group, during one year, and in one region; (c) cumulative risk was similar for vaccinated vs. control children age 2-5years at the end of year 5 and lower for vaccinated vs. control children among older age groups; (d) the protective effect of vaccine against hospitalization decreased from years 1-2 to years 3-5 of follow-up for all age groups and regions.

Risk of Intussusception with Rotavirus Vaccine

OBJECTIVE

To study the case series for intussusception associated with the vaccination of rotavirus vaccine in children.

METHODS

The study of spontaneous adverse event monitoring such as intussusception due to rotavirus vaccine was carried out from the year 2011 through 2015. The individual case safety reports (ICSRs) of this event were collated, assessed and recorded as per the requirement of Suspected Adverse Drug Reactions Reporting form of Pharmacovigilance Programme of India (PvPI).

RESULTS

In the present study, 10 ICSRs of intussussception due to rotavirus vaccine were reported to PvPI. Of which 3 ICSRs were found to be causal relationship with rotavirus vaccine, as evidenced by the adequate information provided in ICSRs.

CONCLUSIONS

Since intussusception, the emerging safety as one of the important safety concern, healthcare professionals are advised to monitor and report to the concerned authority for appropriate action.

Impact of Adverse Events Following Immunization in Viet Nam in 2013 on chronic hepatitis B infection

Adverse Events Following Immunization in Viet Nam in 2013 led to substantial reductions in hepatitis B vaccination coverage (both the birth dose and the three-dose series). In order to estimate the impact of the reduction in vaccination coverage on hepatitis B transmission and future mortality, a widely-used mathematical model was applied to the data from Viet Nam. Using the model, we estimated the number of chronic infections and deaths that are expected to occur in the birth cohort in 2013 and the number of excessive infections and deaths attributable to the drop in immunization coverage in 2013. An excess of 90,137 chronic infections and 17,456 future deaths were estimated to occur in the 2013 birth cohort due to the drop in vaccination coverage. This analysis highlights the importance of maintaining high vaccination coverage and swiftly responding to reported Adverse Events Following Immunization in order to regain consumer confidence in the hepatitis B vaccine.

Introducing seasonal influenza vaccine in low-income countries: an adverse events following immunization survey in the Lao People's Democratic Republic

Objective

In 2012, Lao PDR introduced seasonal influenza vaccine in pregnant women, persons aged ≥50 years, persons with chronic diseases, and healthcare personnel. We assessed adverse events following immunization (AEFI).

Methods

We used a multistage randomized cluster sample design to interview vaccine recipients.

Findings

Between April and May 2012, 355 902 were vaccinated. Of 2089 persons interviewed, 261 (12·5%) reported one or more AEFI. The most commonly reported AEFIs were local reactions. No hospitalizations or deaths were reported; 16% sought medical care. Acceptance and awareness of vaccination were high.

Conclusions

Following the introduction of seasonal influenza vaccine in Lao PDR, self-reported adverse events were mild.

Active surveillance of adverse events following childhood immunization in Singapore

INTRODUCTION

In Singapore, reporting of adverse events following immunization (AEFI) was historically passive. In 2009, Health Sciences Authority collaborated with KK Women's and Children's Hospital to perform active surveillance for AEFI. We report the methodology and initial findings of this surveillance following childhood vaccines.

METHODS

From April 2010 to March 2012, we screened all paediatric admissions for possible relationships to vaccination, excluding elective admissions, and performed causality assessment for each case using standardized definitions for certain, probable, possible and unlikely. Baseline demographics, data on implicated vaccines and clinical details including severity and outcomes were collected. Total hospital admissions were used to calculate rates of AEFI.

RESULTS

We screened 45,571 (80%) of 56,526 admissions, and evaluated 1988 (4.4%) children. Median age at presentation was 3.1 months, while median interval from vaccination to symptom onset was 6 days. There were 311 (15.6%) children with AEFI that were considered possibly, probably or certainly associated with vaccines. However, 98.8% recovered without any long-term sequelae. The hospital-based active surveillance of AEFI enabled the detection of a 5-fold increase (95% CI 1.2-33.1) in BCG-associated regional lymphadenitis in April 2010, which triggered follow-up safety analysis to guide public health advice.

CONCLUSIONS

Hospital-based active surveillance can enhance signal detection and follow-up investigations of AEFI. Subsequently, public health bodies are better equipped to maintain public confidence in vaccination programmes and physicians are able to provide relevant advice to parents. It also allows for a better understanding of risk-benefit ratios of specific vaccines and aids the generation of public health vaccination policy.

Evaluation of the feasibility of a state-based vaccine safety advice network

The vaccine safety advice network is a collaborative pilot project between Vanderbilt University Medical Center, the Tennessee Department of Health, and the Centers for Disease Control and Prevention to assess the feasibility of addressing vaccine safety questions posed by healthcare providers in near real-time. Using a two-tier response system and an electronic database for query submission, the pilot project received ten queries in three and one half months. Two of three pre-specified benchmarks for program evaluation, addressing queries within 24 h of receipt and 100% provider satisfaction, were met; one benchmark, the percentage of questions addressed by Tier 1 staff, was not met. Limitations included few submitted queries primarily involving children in the pilot period, "after-only" program evaluation, and limited geographic generalizability. The study demonstrates a successful partnership between federal, state and academic institutions and a feasible method to respond to healthcare provider inquiries about vaccine safety in near real-time.

Management of vaccine safety in Korea

Although vaccination is regarded as one of the most effective public health measure to prevent and control infectious diseases, no vaccine is perfectly safe. Therefore, safety management is an essential component in running National Immunization Program. Here, we review the current issues and suggest future perspectives of Korean vaccine safety management system.