Evaluation of mRNA-1273 Vaccine in Children 6 Months to 5 Years of Age

A SARS-CoV-2 recombinant spike protein vaccine (S-268019-b) for COVID-19 prevention during the Omicron-dominant period: A phase 3, randomised, placebo-controlled clinical trial

Clinical trials of new vaccines based on existing variants of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) are often impacted by the emergence of new virus variants. We evaluated the efficacy, immunogenicity, and safety of S-268019-b, a recombinant spike protein subunit vaccine based on the ancestral strain, for preventing symptomatic coronavirus disease 2019 (COVID-19) during the Omicron (BA.2)-dominant period in Vietnam. In this multicentre, phase 3, randomised (2:1), observer-blind, placebo-controlled crossover study, participants received 2 intramuscular doses (28 days apart) of either 10 µg of S-268019-b (Recombinant S-protein vaccine) or placebo. The primary endpoint was incidence of laboratory-confirmed symptomatic COVID-19 before crossover, with onset within 14 days following the second dose, in participants who were seronegative and reverse transcription polymerase chain reaction (RT-PCR)-negative at baseline. The secondary endpoints included immunogenicity and safety. In total, 8,594 participants were randomised (S-268019-b [n = 5,727]; placebo [n = 2,867]). Vaccine efficacy versus placebo was 39·1 % (95 % confidence interval [CI]:26·6-49·5; one-sided P = 0·0723). The incidence rate (95 % CI) of symptomatic COVID-19 was 776·41/1,000 person-years (682·04-880·19) in the S-268019-b group and 1272·87/1,000 person-years (1101·32-1463·57) in the placebo group. The geometric mean titres (95 % CI) of the SARS-CoV-2 neutralising antibody increased on Day 57 versus baseline with S-268019-b (34·66 [27·04-44·41] versus 2·50 (non-estimable) but not with placebo. There were no safety concerns regarding S-268019-b. S-268019-b did not demonstrate the targeted efficacy threshold against symptomatic COVID-19; however, findings were comparable with other prophylactic vaccines based on ancestor strain during the Omicron-dominant period. S-268019-b demonstrated immunogenicity and was well-tolerated. ClinicalTrials.gov identifier: NCT05212948.

Safety and Immunogenicity of an mRNA-Based hMPV/PIV3 Combination Vaccine in Seropositive Children

OBJECTIVES

Human metapneumovirus (hMPV) and parainfluenza virus type 3 (PIV3) are common respiratory illnesses in children. The safety and immunogenicity of an investigational mRNA-based vaccine, mRNA-1653, encoding membrane-anchored fusion proteins of hMPV and PIV3, was evaluated in hMPV/PIV3-seropositive children.

METHODS

In this phase 1b randomized, observer-blind, placebo-controlled, dose-ranging study, hMPV/PIV3-seropositive children were enrolled sequentially into 2 dose levels of mRNA-1653 administered 2 months apart; children aged 12 to 36 months were randomized (1:1) to receive 10-μg of mRNA-1653 or placebo and children aged 12 to 59 months were randomized (3:1) to receive 30-μg of mRNA-1653 or placebo.

RESULTS

Overall, 27 participants aged 18 to 55 months were randomized; 15 participants received 10-μg of mRNA-1653 (n = 8) or placebo (n = 7), whereas 12 participants received 30-μg of mRNA-1653 (n = 9) or placebo (n = 3). mRNA-1653 was well-tolerated at both dose levels. The only reported solicited local adverse reaction was tenderness at injection site; solicited systemic adverse reactions included grade 1 or 2 chills, irritability, loss of appetite, and sleepiness. A single 10-μg or 30-μg mRNA-1653 injection increased hMPV and PIV3 neutralizing antibody titers (geometric mean fold-rise ratio over baseline: hMPV-A = 2.9-6.1; hMPV-B = 6.2-13.2; PIV3 = 2.8-3.0) and preF and postF binding antibody concentrations (geometric mean fold-rise ratio: hMPV preF = 5.3-6.1; postF = 4.6-6.5 and PIV3 preF = 13.9-14.2; postF = 11.0-12.1); a second injection did not further increase antibody levels in these seropositive children. Binding antibody responses were generally preF biased.

CONCLUSIONS

mRNA-1653 was well-tolerated and boosted hMPV and PIV3 antibody levels in seropositive children aged 12 to 59 months, supporting the continued development of mRNA-1653 or its components for the prevention of hMPV and PIV3.

Immunogenicity of Monovalent mRNA-1273 and BNT162b2 Vaccines in Children <5 Years of Age

BACKGROUND AND OBJECTIVES

The messenger RNA (mRNA)-based coronavirus disease 2019 vaccines approved for use in children <5 years of age have different antigen doses and administration schedules that could affect vaccine immunogenicity and effectiveness. We sought to compare the strength and breadth of serum binding and neutralizing antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) elicited by monovalent mRNA-based coronavirus disease 2019 vaccines in young children.

METHODS

We conducted a prospective cohort study of children 6 months to 4 years of age who completed primary series vaccination with monovalent mRNA-1273 or BNT162b2 vaccines. Serum was collected 1 month after primary vaccine series completion for the measurement of SARS-CoV-2-specific humoral immune responses, including antibody binding responses to Spike proteins from an ancestral strain (D614G) and major variants of SARS-CoV-2 and antibody neutralizing activity against D614G and Omicron subvariants (BA.1, BA.4/5).

RESULTS

Of 75 participants, 40 (53%) received mRNA-1273 and 35 (47%) received BNT162b2. Children receiving either primary vaccine series developed robust and broad SARS-CoV-2-specific binding and neutralizing antibodies, including to Omicron subvariants. Children with a previous history of SARS-CoV-2 infection developed significantly higher antibody binding responses and neutralization titers to Omicron subvariants, which is consistent with the occurrence of identified infections during the circulation of Omicron subvariants in the region.

CONCLUSIONS

Monovalent mRNA-1273 and BNT162b2 elicited similar antibody responses 1 month after vaccination in young children. In addition, previous infection significantly enhanced the strength of antibody responses to Omicron subvariants. The authors of future studies should evaluate incorporation of these vaccines into the standard childhood immunization schedule.

Association of New-Onset Seizures With SARS-CoV-2 Vaccines: A Systematic Review and Meta-Analysis of Randomized Clinical Trials

Importance

Seizures have been reported as an adverse effect of the SARS-CoV-2 vaccine. However, no study has answered the question of whether there is any association between seizures in the general population and COVID-19 vaccination.

Objective

To evaluate the seizure incidence among SARS-CoV-2 vaccine recipients compared with those who received a placebo.

Data Sources

A systematic search of MEDLINE (via PubMed), Web of Science, Scopus, Cochrane Library, Google Scholar, review publications, editorials, letters to editors, and conference papers, along with the references of the included studies from December 2019 to July 7, 2023.

Study Selection

Randomized clinical trials (RCTs) reporting seizure incidence with SARS-CoV-2 vaccination were included.

Data Extraction and Synthesis

This study is reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses framework and used the Mantel-Haenszel method with random- and common-effect models. The risk of bias of the studies was assessed using the Cochrane assessment tool for RCTs.

Main Outcomes and Measures

The outcome of interest was new-onset seizure incidence proportion compared among (1) SARS-CoV-2 vaccine recipients and (2) placebo recipients.

Results

Six RCTs were included in the study. Results of the pooled analysis comparing the incidence of new-onset seizure between the 63 521 vaccine and 54 919 placebo recipients in the 28-day follow-up after vaccine/placebo injection showed no statistically significant difference between the 2 groups (9 events [0.014%] in vaccine and 1 event [0.002%] in placebo recipients; odds ratio [OR], 2.70; 95% CI, 0.76-9.57; P = .12; I2 = 0%, τ2 = 0, Cochran Q P = .74). Likewise, in the entire blinded-phase period after injection, with a median of more than 43 days, no significant difference was identified between the vaccine and placebo groups regarding incident new-onset seizure (13/43 724 events [0.03%] in vaccine and 5/40 612 [0.012%] in placebo recipients; OR, 2.31; 95% CI, 0.86-3.23, P > .99, I2 = 0%, τ2 = 0, Cochran Q P = .95).

Conclusions and Relevance

According to this systematic review and meta-analysis, there was no statistically significant difference in the risk of new-onset seizure incidence between vaccinated individuals and placebo recipients.

Monovalent SARS-CoV-2 mRNA Vaccine Does not Boost Omicron-Specific Immune Response in Diabetic and Control Pediatric Patients

While the immunogenicity of SARS-CoV-2 vaccines has been well described in adults, pediatric populations have been less studied. In particular, children with type 1 diabetes are generally at elevated risk for more severe disease after infections, but are understudied in terms of COVID-19 and SARS-CoV-2 vaccine responses. We investigated the immunogenicity of COVID-19 mRNA vaccinations in 35 children with type 1 diabetes (T1D) and 23 controls and found that these children develop levels of SARS-CoV-2 neutralizing antibody titers and spike protein-specific T cells comparable to nondiabetic children. However, in comparing the neutralizing antibody responses in children who received 2 doses of mRNA vaccines (24 T1D; 14 controls) with those who received a third, booster dose (11 T1D; 9 controls), we found that the booster dose increased neutralizing antibody titers against ancestral SARS-CoV-2 strains but, unexpectedly, not Omicron lineage variants. In contrast, boosting enhanced Omicron variant neutralizing antibody titers in adults.

Effectiveness of inactivated COVID-19 vaccine CoronaVac in children aged less than 3 years old during Omicron wave in Hong Kong

The COVID-19 pandemic has affected people of all ages worldwide. However, there is still no information on the vaccine effectiveness (VE) of inactivated COVID-19 vaccines in children aged less than 3 years old. This study highlighted that 2 doses of CoronaVac were effective in preventing COVID-19, with a VE of 83.1 %.

Interim safety and immunogenicity of COVID-19 omicron BA.1 variant-containing vaccine in children in the USA: an open-label non-randomised phase 3 trial

BACKGROUND

Variant-containing mRNA vaccines for COVID-19 to broaden protection against SARS-CoV-2 variants are recommended based on findings in adults. We report interim safety and immunogenicity of an omicron BA.1 variant-containing (mRNA-1273.214) primary vaccination series and booster dose in paediatric populations.

METHODS

This open-label, two-part, non-randomised phase 3 trial enrolled participants aged 6 months to 5 years at 24 US study sites. Eligible participants were generally healthy or had stable chronic conditions, without known SARS-CoV-2 infection in the previous 90 days. Individuals who were acutely ill or febrile 1 day before or at the screening visit or those who previously received other COVID-19 vaccines (except mRNA-1273 for part 2) were excluded. In part 1, SARS-CoV-2-vaccine-naive participants received two-dose mRNA-1273.214 (25 μg; omicron BA.1 and ancestral Wuhan-Hu-1 mRNA) primary series. In part 2, participants who previously completed the two-dose mRNA-1273 (25 μg) primary series in KidCOVE (NCT04796896) received a mRNA-1273.214 (10 μg) booster dose. Primary study outcomes were safety and reactogenicity of the mRNA-1273.214 primary series (part 1) or booster dose (part 2) as well as the inferred effectiveness of mRNA-1273.214 based on immune responses against ancestral SARS-CoV-2 (D614G) and omicron BA.1 variant at 28 days post-primary series (part 1) or post-booster dose (part 2). The safety set included participants who received at least one dose of the study vaccine; the immunogenicity set included those who provided immunogenicity samples. Interim safety and immunogenicity are summarised in this analysis as of the data cutoff date (Dec 5, 2022). This trial is registered with ClinicalTrials.gov, NCT05436834.

FINDINGS

Between June 21, 2022, and Dec 5, 2022, 179 participants received one or more doses of mRNA-1273.214 primary series (part 1) and 539 received a mRNA-1273.214 booster dose (part 2). The safety profile within 28 days after either dose of the mRNA-1273.214 primary series and the booster dose was consistent with that of the mRNA-1273 primary series in this age group, with no new safety concerns or vaccine-related serious adverse events observed. At 28 days after primary series dose 2 and the booster dose, both mRNA-1273.214 primary series (day 57, including all participants with or without evidence of prior SARS-CoV-2 infection at baseline) and booster (day 29, including participants without evidence of prior SARS-CoV-2 infection at baseline) elicited responses that were superior against omicron-BA.1 (geometric mean ratio part 1: 25·4 [95% CI 20·1-32·1] and part 2: 12·5 [11·0-14·3]) and non-inferior against D614G (part 1: 0·8 [0·7-1·0] and part 2: 3·1 [2·8-3·5]), compared with neutralising antibody responses induced by the mRNA-1273 primary series (in a historical comparator group).

INTERPRETATION

mRNA-1273.214 was immunogenic against BA.1 and D614G in children aged 6 months to 5 years, with a comparable safety profile to mRNA-1273, when given as a two-dose primary series or a booster dose. These results are aligned with the US Centers for Disease Control and Prevention recommendations for the use of variant-containing vaccines for continued protection against the emerging variants of SARS-CoV-2.

FUNDING

Moderna.

Effectiveness of mRNA BNT162b2 and inactivated CoronaVac vaccines against severe COVID-19 outcomes among non-hospitalised children aged 1-3 years with SARS-CoV-2 Omicron infection

OBJECTIVES

Clinical evidence on the effectiveness of COVID-19 vaccines for children aged 1-3 years is scarce. The effectiveness of COVID-19 vaccines was evaluated among non-hospitalised children aged 1-3 years with SARS-CoV-2 Omicron infection in Hong Kong.

METHODS

A retrospective cohort of all non-hospitalised children aged 1-3 years with confirmed SARS-CoV-2 infection between 4 August 2022 and 29 January 2023 in Hong Kong was analysed. Vaccinated group was defined as the recipients of one or more doses of CoronaVac or mRNA vaccine BNT162b2 (original, monovalent) at least 14 days prior to infection. Hazard ratios (HR) with 95% confidence intervals (95% CI) of study outcomes were estimated using Cox regression models. Effectiveness outcomes included 28-day all-cause mortality and COVID-19-related hospitalisation.

RESULTS

A total of 5552 vaccinated patients and 5552 propensity-score matched controls (unvaccinated patients) were included for analysis. The cumulative incidence of COVID-19-related hospitalisation over 28 days was 2.3% and 2.9% in the vaccinated and control groups, respectively. There were no deaths in both groups. COVID-19 vaccination was associated with a significant reduction in 28-day COVID-19-related hospitalisation risk (HR=0.785, 95% CI=0.626-0.985, P=0.037), particularly for children aged 3 years, those who had received two or more vaccine doses, and those who received CoronaVac as the last dose.

CONCLUSION

COVID-19 vaccination is associated with a significantly lower risk of 28-day COVID-19-related hospitalisation among infected children aged 1-3 years, particularly those who had received two or more vaccine doses. This observation emphasises the importance of completing the full two-dose or three-dose series to optimise vaccine effectiveness.

Characteristics and Clinical Outcomes of Vaccine-Eligible US Children Under-5 Years Hospitalized for Acute COVID-19 in a National Network

BACKGROUND AND OBJECTIVES

In June 2022, the mRNA COVID-19 vaccination was recommended for young children. We examined clinical characteristics and factors associated with vaccination status among vaccine-eligible young children hospitalized for acute COVID-19.

METHODS

We enrolled inpatients 8 months to <5 years of age with acute community-acquired COVID-19 across 28 US pediatric hospitals from September 20, 2022 to May 31, 2023. We assessed demographic and clinical factors, including the highest level of respiratory support, and vaccination status defined as unvaccinated, incomplete, or complete primary series [at least 2 (Moderna) or 3 (Pfizer-BioNTech) mRNA vaccine doses ≥14 days before hospitalization].

RESULTS

Among 597 children, 174 (29.1%) patients were admitted to the intensive care unit and 75 (12.6%) had a life-threatening illness, including 51 (8.5%) requiring invasive mechanical ventilation. Children with underlying respiratory and neurologic/neuromuscular conditions more frequently received higher respiratory support. Only 4.5% of children hospitalized for COVID-19 (n = 27) had completed their primary COVID-19 vaccination series and 7.0% (n = 42) of children initiated but did not complete their primary series. Among 528 unvaccinated children, nearly half (n = 251) were previously healthy, 3 of them required extracorporeal membrane oxygenation for acute COVID-19 and 1 died.

CONCLUSIONS

Most young children hospitalized for acute COVID-19, including most children admitted to the intensive care unit and with life-threatening illness, had not initiated COVID-19 vaccination despite being eligible. Nearly half of these children had no underlying conditions. Of the small percentage of children who initiated a COVID-19 primary series, most had not completed it before hospitalization.

Benefit-Risk Assessment of mRNA COVID-19 Vaccines in Children Aged 6 Months to 4 Years in the Omicron Era

BACKGROUND

There is no risk and benefit assessment of COVID-19 vaccination for children younger than 5 years using a single health outcomes scale. The objective of this study is to compare the expected risk and benefits of the mRNA primary series of COVID-19 vaccines for children aged 6 months to 4 years in the United States using a single health outcome scale in the Omicron era.

METHODS

The expected benefits and risks of the primary two-dose series of mRNA COVID-19 vaccines for children aged 6 months to 4 years were stratified by sex, the presence of underlying medical conditions, the presence of infection-induced immunity, and the type of mRNA vaccine (BNT162b2 or mRNA-1273). A scoping literature review was conducted to identify the indicators in the decision tree model. The benefit-risk ratio was the outcome of interest.

RESULTS

The benefit-risk ratios ranged from 200.4 in BNT162b2 for males aged 6-11 months with underlying medical conditions and without infection-induced immunity to 3.2 in mRNA-1273 for females aged 1-4 years without underlying medical conditions and with infection-induced immunity.

CONCLUSIONS

The expected benefit of receiving the primary series of mRNA vaccines outweighed the risk among children ages 6 months to 4 years regardless of sex, presence of underlying medical conditions, presence of infection-induced immunity, or type of mRNA vaccines. However, the continuous monitoring of the COVID-19 epidemiology as well as vaccine effectiveness and safety is important.

Comparative efficacy and safety of COVID-19 vaccines in phase III trials: a network meta-analysis

BACKGROUND

Over a dozen vaccines are in or have completed phase III trials at an unprecedented speed since the World Health Organization (WHO) declared COVID-19 a pandemic. In this review, we aimed to compare and rank these vaccines indirectly in terms of efficacy and safety using a network meta-analysis.

METHODS

We searched Embase, MEDLINE, and the Cochrane Library for phase III randomized controlled trials (RCTs) from their inception to September 30, 2023. Two investigators independently selected articles, extracted data, and assessed the risk of bias. Outcomes included efficacy in preventing symptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and the incidence of serious adverse events (SAEs) according to vaccine type and individual vaccines in adults and elderly individuals. The risk ratio and mean differences were calculated with 95% confidence intervals using a Bayesian network meta-analysis.

RESULTS

A total of 25 RCTs involving 22 vaccines were included in the study. None of vaccines had a higher incidence of SAEs than the placebo. Inactivated virus vaccines might be the safest, with a surface under the cumulative ranking curve (SUCRA) value of 0.16. BIV1-CovIran showed the highest safety index (SUCRA value: 0.13), followed by BBV152, Soberana, Gam-COVID-Vac, and ZF2001. There were no significant differences among the various types of vaccines regarding the efficacy in preventing symptomatic SARS-CoV-2 infection, although there was a trend toward higher efficacy of the mRNA vaccines (SUCRA value: 0.09). BNT162b2 showed the highest efficacy (SUCRA value: 0.02) among the individual vaccines, followed by mRNA-1273, Abdala, Gam-COVID-Vac, and NVX-CoV2373. BNT162b2 had the highest efficacy (SUCRA value: 0.08) in the elderly population, whereas CVnCoV, CoVLP + AS03, and CoronaVac were not significantly different from the placebo.

CONCLUSIONS

None of the different types of vaccines were significantly superior in terms of efficacy, while mRNA vaccines were significantly inferior in safety to other types. BNT162b2 had the highest efficacy in preventing symptomatic SARS-CoV-2 infection in adults and the elderly, whereas BIV1-CovIran had the lowest incidence of SAEs in adults.

COVID-19 booster enhances IgG mediated viral neutralization by human milk in vitro

Background

Facilitated by the inability to vaccinate, and an immature immune system, COVID-19 remains a leading cause of death among children. Vaccinated lactating mothers produce specific SARS-CoV-2 antibodies in their milk, capable of neutralizing the virus in vitro. Our objective for this study is to assess the effect of COVID-19 booster dose on SARS-CoV-2 antibody concentration and viral neutralization in milk, plasma, and infant stool.

Methods

Thirty-nine mothers and 25 infants were enrolled from December 2020 to May 2022. Milk, maternal plasma, and infants' stool were collected at various time-points up to 12 months following mRNA COVID-19 vaccination. A subgroup of 14 mothers received a booster dose. SARS-CoV-2 antibody levels and their neutralization capacities were assessed.

Results

Booster vaccination led to significantly higher IgG levels within human milk and breastfed infants' stool. In vitro neutralization of VSV-gfp-SARS-CoV-2-S-gp, a laboratory safe SARS-CoV-2 like pseudovirus, improved following the booster, with a 90% increase in plasma neutralization and a 60% increase in milk neutralization. We found that post-booster neutralization by human milk was highly correlated to SARS-CoV-2 IgG level. In support of our correlation result, Protein G column depletion of IgG in milk yielded a significant reduction in viral neutralization (p = 0.04).

Discussion

The substantial increase in neutralizing IgG levels in milk and breastfed infants' stool post-booster, coupled with the decrease in milk neutralization capabilities upon IgG depletion, underscores the efficacy of booster doses in augmenting the immune response against SARS-CoV-2 in human milk.

Humoral profiles of toddlers and young children following SARS-CoV-2 mRNA vaccination

Although young children generally experience mild symptoms following infection with SARS-CoV-2, severe acute and long-term complications can occur. SARS-CoV-2 mRNA vaccines elicit robust immunoglobulin profiles in children ages 5 years and older, and in adults, corresponding with substantial protection against hospitalizations and severe disease. Whether similar immune responses and humoral protection can be observed in vaccinated infants and young children, who have a developing and vulnerable immune system, remains poorly understood. To study the impact of mRNA vaccination on the humoral immunity of infant, we use a system serology approach to comprehensively profile antibody responses in a cohort of children ages 6 months to 5 years who were vaccinated with the mRNA-1273 COVID-19 vaccine (25 μg). Responses are compared with vaccinated adults (100 μg), in addition to naturally infected toddlers and young children. Despite their lower vaccine dose, vaccinated toddlers elicit a functional antibody response as strong as adults, with higher antibody-dependent phagocytosis compared to adults, without report of side effects. Moreover, mRNA vaccination is associated with a higher IgG3-dependent humoral profile against SARS-CoV-2 compared to natural infection, supporting that mRNA vaccination is effective at eliciting a robust antibody response in toddlers and young children.

Attitudes Toward Routine Vaccines and COVID-19 Vaccines Among Parents of Infants and Toddlers in an Urban Safety-Net Setting

This study explores attitudes toward diphtheria-tetanus-acellular pertussis (DTaP), measles-mumps-rubella (MMR), influenza, and coronavirus disease 2019 (COVID-19) vaccines among English-speaking and Spanish-speaking parents of infants in a safety-net setting. Parents aged 18 years or older were recruited from outpatient clinics between December 2020 and December 2021. The interviews were then recorded, transcribed, translated, and qualitatively analyzed using the modified grounded theory. Thirty-two individuals participated (18 English-speaking and 14 Spanish-speaking). Almost all supported receiving routine childhood vaccines, DTaP, influenza, and MMR and believed that vaccines promote health. Vaccine concerns differed by each vaccine. Few participants expressed concerns about DTaP and MMR vaccines. Concerns around influenza vaccines often stemmed from personal experience and perceived increased risk of flu-like illnesses. Participants expressed the most concerns related to COVID-19 vaccinations, including age-based immunity of their infants. Based on these findings, future interventions to improve vaccine uptake may focus on benefits common to all vaccines, while addressing vaccine-specific concerns.

Effect of Platform Type on Clinical Efficacy of SARS-CoV-2 Vaccines in Prime Vaccination Settings: A Systematic Review and Meta-Regression of Randomized Controlled Trials

This systematic review investigated the association between platform type and the clinical efficacy of SARS-CoV-2 vaccines using the meta-regression of randomized controlled trials to compare the rates of the first appearance of symptomatic COVID-19 on the platforms. The trial search was conducted using PubMed, ClinicalTrials.gov, and the EU Clinical Trials Register. The main selection criteria included: non-active control, immunocompetent individuals without previous vaccination, and a low risk of bias. The platform effect was summarized with an incidence rate ratio (IRR) and a 95% confidence interval for every platform category against the reference. IRR was obtained by random-effect meta-regression with adjustment for confounding by effect modifiers. The analysis was conducted in per-protocol (PP) and modified intention-to-treat (mITT) sets. Six vaccine types with 35 trials were included. Vector vaccines were a reference category. In the PP set, rates of symptomatic COVID-19 on mRNA and protein subunit vaccines were significantly lower than on the vector: IRR = 0.30 [0.19; 0.46], p = 0.001 and 0.63 [0.46; 0.86], p = 0.012, respectively. There was no difference for inactivated and virus-like particle vaccines compared to the vector: IRR = 0.98 [0.71; 1.36], p = 0.913 and 0.70 [0.41; 1.20], p = 0.197, respectively. The rate of cases on DNA vaccines was significantly higher than that on the vector: IRR = 2.58 [1.17; 5.68], p = 0.034. Results for the mITT set were consistent. Platform type is an effect modifier of the clinical efficacy of SARS-CoV-2 vaccines.

Emerging and re-emerging pediatric viral diseases: a continuing global challenge

The twenty-first century has been marked by a surge in viral epidemics and pandemics, highlighting the global health challenge posed by emerging and re-emerging pediatric viral diseases. This review article explores the complex dynamics contributing to this challenge, including climate change, globalization, socio-economic interconnectedness, geopolitical tensions, vaccine hesitancy, misinformation, and disparities in access to healthcare resources. Understanding the interactions between the environment, socioeconomics, and health is crucial for effectively addressing current and future outbreaks. This scoping review focuses on emerging and re-emerging viral infectious diseases, with an emphasis on pediatric vulnerability. It highlights the urgent need for prevention, preparedness, and response efforts, particularly in resource-limited communities disproportionately affected by climate change and spillover events. Adopting a One Health/Planetary Health approach, which integrates human, animal, and ecosystem health, can enhance equity and resilience in global communities. IMPACT: We provide a scoping review of emerging and re-emerging viral threats to global pediatric populations This review provides an update on current pediatric viral threats in the context of the COVID-19 pandemic This review aims to sensitize clinicians, epidemiologists, public health practitioners, and policy stakeholders/decision-makers to the role these viral diseases have in persistent pediatric morbidity and mortality.

Development of COVID-19 vaccine policy - United States, 2020-2023

COVID-19 vaccines represent a great scientific and public health achievement in the face of overwhelming pressures from a global pandemic, preventing millions of hospitalizations and deaths due to COVID-19 vaccines in the United States. Over 675 million doses of COVID-19 vaccines have been administered in the United States, and over 80% of the U.S. population has had at least 1 dose of a COVID-19 vaccine. Over the course of the COVID-19 pandemic in the United States, over one million people died from COVID-19, and over six million were hospitalized. It has been estimated that COVID-19 vaccines prevented more than 18 million additional hospitalizations and more than 3 million additional deaths due to COVID-19 in the United States. From the beginning of the COVID-19 pandemic in 2020 through June 2023, ACIP had 35 COVID-19 focused meetings and 24 votes for COVID-19 vaccine recommendations. ACIP had the critical task of rapidly and thoroughly reviewing emerging and evolving data on COVID-19 epidemiology and vaccines, as well as making comprehensive population-based recommendations for vaccine policy and considerations for implementation through a transparent and evidence-based framework. Safe and effective COVID-19 vaccines, recommended through transparent policy discussions with ACIP, remain the best tool we have to prevent serious illness, hospitalization and death from COVID-19.

COVID-19 Vaccines in Children

The COVID-19 pandemic has left an indelible mark on global health, affecting individuals of all ages across diverse communities. While the virus has predominantly been associated with severe outcomes in adults, its impact on children has garnered increasing attention. Today, three COVID-19 vaccines are available for use in the U.S. and recommended by the Advisory Committee on Immunization Practices (ACIP). As of September 2023, ongoing genomic surveillance identified SARS-CoV-2 XBB sublineages as the most common circulating SARS-CoV-2 variants, constituting over 99% of sequenced SARS-CoV-2 specimens in the US. Recently, recommendations for COVID-19 vaccination were updated accordingly to the 2023-2024 Omicron-XBB.1.5-adapted monovalent COVID-19 vaccine to provide heightened protection against currently circulating SARS-CoV-2 XBB-sublineage variants. COVID-19 vaccines have proven to be safe, efficacious, and effective at protecting against COVID-19 and preventing severe illness in children and adolescents.

Safety and efficacy of the intranasal spray SARS-CoV-2 vaccine dNS1-RBD: a multicentre, randomised, double-blind, placebo-controlled, phase 3 trial

BACKGROUND

The live-attenuated influenza virus vector-based intranasal SARS-CoV-2 vaccine (dNS1-RBD, Pneucolin; Beijing Wantai Biological Pharmacy Enterprise, Beijing, China) confers long-lasting and broad protection in animal models and is, to our knowledge, the first COVID-19 mucosal vaccine to enter into human trials, but its efficacy is still unknown. We aimed to assess the safety and efficacy (but not the immunogenicity) of dNS1-RBD against COVID-19.

METHODS

We did a multicentre, randomised, double-blind, placebo-controlled, adaptive design, phase 3 trial at 33 centres (private or public hospitals, clinical research centres, or Centre for Disease Control and Prevention) in four countries (Colombia, Philippines, South Africa, and Viet Nam). Men and non-pregnant women (aged ≥18 years) were eligible if they had never been infected with SARS-CoV-2, and if they did not have a SARS-CoV-2 vaccination history at screening or if they had received at least one dose of other SARS-CoV-2 vaccines 6 months or longer before enrolment. Eligible adults were randomly assigned (1:1) to receive two intranasal doses of dNS1-RBD or placebo administered 14 days apart (0·2 mL per dose; 0·1 mL per nasal cavity), with block randomisation via an interactive web-response system, stratified by centre, age group (18-59 years or ≥60 years), and SARS-CoV-2 vaccination history. All participants, investigators, and laboratory staff were masked to treatment allocation. The primary outcomes were safety of dNS1-RBD in the safety population (ie, those who had received at least one dose of dNS1-RBD or placebo) and efficacy against symptomatic SARS-CoV-2 infection confirmed by RT-PCR occurring 15 days or longer after the second dose in the per-protocol population (ie, those who received two doses, were followed up for 15 days or longer after the second dose, and had no major protocol deviations). The success criterion was predefined as vaccine efficacy of more than 30%. This trial is registered with the Chinese Clinical Trial Registry (ChiCTR2100051391) and is completed.

FINDINGS

Between Dec 16, 2021, and May 31, 2022, 41 620 participants were screened for eligibility and 31 038 participants were enrolled and randomly assigned (15 517 in the vaccine group and 15 521 in the placebo group). 30 990 participants who received at least one dose (15 496 vaccine and 15 494 placebo) were included in the safety analysis. The results showed a favourable safety profile, with the most common local adverse reaction being rhinorrhoea (578 [3·7%] of 15 500 vaccine recipients and 546 [3·5%] of 15 490 placebo recipients) and the most common systemic reaction being headache (829 [5·3%] vaccine recipients and 797 [5·1%] placebo recipients). We found no differences in the incidences of adverse reactions between participants in the vaccine and placebo groups. No vaccination-related serious adverse events or deaths were observed. Among 30 290 participants who received two doses, 25 742 were included in the per-protocol efficacy analysis (12 840 vaccine and 12 902 placebo). The incidence of confirmed symptomatic SARS-CoV-2 infection caused by omicron variants regardless of immunisation history was 1·6% in the vaccine group and 2·3% in the placebo group, resulting in an overall vaccine efficacy of 28·2% (95% CI 3·4-46·6), with a median follow-up duration of 161 days.

INTERPRETATION

Although this trial did not meet the predefined efficacy criteria for success, dNS1-RBD was well tolerated and protective against omicron variants, both as a primary immunisation and as a heterologous booster.

FUNDING

Beijing Wantai Biological Pharmacy Enterprise, National Science and Technology Major Project, National Natural Science Foundation of China, Fujian Provincial Science and Technology Plan Project, Natural Science Foundation of Fujian Province, Xiamen Science and Technology Plan Special Project, Bill & Melinda Gates Foundation, the Ministry of Education of China, Xiamen University, and Fieldwork Funds of Xiamen University.

Effectiveness of Monovalent mRNA Vaccines Against Omicron XBB Infection in Singaporean Children Younger Than 5 Years

Importance

Literature on vaccine effectiveness of SARS-CoV-2 messenger RNA (mRNA) vaccines for children younger than 5 years is limited.

Objective

To report the effectiveness of monovalent mRNA vaccines against SARS-CoV-2 infection among Singaporean children aged 1 through 4 years during a COVID-19 pandemic wave of the Omicron XBB variant.

Design, Setting, and Participants

This was a population-based cohort study, conducted over a 6-month study period from October 1, 2022, through March 31, 2023, after the implementation of community vaccination among all Singaporean children aged 1 through 4 years. The study period was dominated by the Omicron XBB subvariant.

Exposure

Receipt of SARS-CoV-2 mRNA vaccines.

Main Outcome Measure

Vaccine effectiveness against confirmed SARS-CoV-2 infection. The adjusted incidence rate ratio for confirmed infections using Poisson regression was reported, with the reference group being those who were unvaccinated. Analyses were stratified by prior documented SARS-CoV-2 infection.

Results

A total of 121 628 children (median [IQR] age, 3.1 [2.2-3.9] years; 61 925 male [50.9%]) were included in the study, contributing 21 015 956 person-days of observation. The majority of children (11 294 of 11 705 [96.5%]) received the mRNA-1273 COVID-19 vaccine (Moderna). Vaccine effectiveness against confirmed infection was 45.2% (95% CI, 24.7%-60.2%) in partially vaccinated, infection-naive children and 63.3% (95% CI, 40.6%-77.3%) in fully vaccinated, infection-naive children compared with the unvaccinated group. Among previously infected children, vaccine effectiveness against reinfections in those with at least 1 vaccine dose was estimated at 74.6% (95% CI, 38.7%-89.5%).

Conclusions and Relevance

Study results suggest that completion of a primary mRNA vaccine series provided protection against SARS-CoV-2 infection in children aged 1 through 4 years. Although incidence of hospitalization and severe illness is low in this age group, there is potential benefit of vaccination in preventing infection and potential sequelae.

Successful treatment of fulminant myocarditis due to COVID-19 in a 5-year-old girl

Reports of acute myocarditis are increasing due to the worldwide spread of coronavirus disease 2019 (COVID-19). We report a case of a 5-year-old girl with fulminant myocarditis caused by COVID-19, who was successfully treated with veno-arterial extracorporeal membrane oxygenation (VA-ECMO). The unvaccinated patient had developed fever 1 week before attending our hospital and was "presumptive positive" for COVID-19 based on the surrounding infectious situation. The fever resolved, but the day before the visit, abdominal pain appeared. The patient visited her previous physician with vomiting as the main complaint. She was transferred to our hospital due to impaired consciousness and bradycardia, with a heart rate of 40 beats/min. Immediately after transfer, she was diagnosed with complete atrioventricular (AV) block and was scheduled to undergo percutaneous pacing lead insertion. However, the patient had ventricular tachycardia, AV block and hypotension intraoperatively and required cardiopulmonary resuscitation. The patient was in an extremely unstable circulatory state, and VA-ECMO was urgently introduced. After multidisciplinary treatment for acute myocarditis, waiting for an improvement in AV block, and recovery of cardiac function, the patient was weaned from VA-ECMO on the eighth day after admission. The patient was discharged with no cardiac or neurologic sequelae.

Learning objective

The rapid introduction of veno-arterial extracorporeal membrane oxygenation for fulminant myocarditis caused by coronavirus disease 2019 (COVID-19) in young children is extremely effective. Vaccination may be important for preventing infection with COVID-19 and avoiding severe complications.

Clinical Syndromes Related to SARS-CoV-2 Infection and Vaccination in Pediatric Age: A Narrative Review

This narrative review aims to report the main clinical manifestations, therapeutic strategies, outcomes, and complications of acute SARS-CoV-2 infection in childhood and to summarize the data relating the SARS-CoV-2 vaccination efficacy and safety in pediatric age. SARS-CoV-2 infection mostly occurs asymptomatically in the pediatric population, while multisystem inflammatory syndrome in children (MIS-C) represents the most severe coronavirus disease 2019 (COVID-19)-related illness, a life-threatening event with a high morbidity rate. After the development of SARS-CoV-2 vaccines and their subsequent approval in children, the rate of infection as well as the number of its related complications have shown a drastic decrease. Fully vaccinated children are protected from the risk of developing a severe disease and a similar protective role has been observed in the reduction of complications, in particular MIS-C. However, long-lasting immunity has not been demonstrated, booster doses have been required, and reinfection has been observed. With regards to vaccine safety, adverse events were generally mild to moderate in all age groups: local adverse events were the most commonly reported. Nevertheless, a potential association between SARS-CoV-2 vaccine and the subsequent development of inflammatory manifestations has been suggested. Myocarditis has rarely been observed following vaccination; it appeared to be more frequent among adolescent males with a mild clinical course leading to a complete recovery. SARS-CoV-2 vaccine-related MIS-C cases have been described, although a univocal definition and an exact time interval with respect to vaccination has not been reported, thus not establishing a direct causal link. Current evidence about COVID-19 vaccination in children and adolescents suggest that benefits outweigh potential risks. Long-term data collection of the post-authorization safety surveillance programs will better define the real incidence of SARS-CoV-2 vaccine-related complications in the pediatric population.

Effects of COVID-19 vaccination and previous SARS-CoV-2 infection on omicron infection and severe outcomes in children under 12 years of age in the USA: an observational cohort study

BACKGROUND

Data on the protection conferred by COVID-19 vaccination and previous SARS-CoV-2 infection against omicron (B.1.1.529) infection in young children are scarce. We aimed to estimate the time-varying effects of primary and booster COVID-19 vaccination and previous SARS-CoV-2 infection on subsequent omicron infection and severe illness (hospital admission or death) in children younger than 12 years of age.

METHODS

In this observational cohort study, we obtained individual-level records on vaccination with the BNT162b2 and mRNA-1273 vaccines and clinical outcomes from the North Carolina COVID-19 Surveillance System and the COVID-19 Vaccine Management System for 1 368 721 North Carolina residents aged 11 years or younger from Oct 29, 2021 (Oct 29, 2021 for children aged 5-11 years and June 17, 2022 for children aged 0-4 years), to Jan 6, 2023. We used Cox regression to estimate the time-varying effects of primary and booster vaccination and previous infection on the risks of omicron infection, hospital admission, and death.

FINDINGS

For children 5-11 years of age, the effectiveness of primary vaccination against infection, compared with being unvaccinated, was 59·9% (95% CI 58·5-61·2) at 1 month, 33·7% (32·6-34·8) at 4 months, and 14·9% (95% CI 12·3-17·5) at 10 months after the first dose. Compared with primary vaccination only, the effectiveness of a monovalent booster dose after 1 month was 24·4% (14·4-33·2) and that of a bivalent booster dose was 76·7% (45·7-90·0). The effectiveness of omicron infection against reinfection was 79·9% (78·8-80·9) after 3 months and 53·9% (52·3-55·5) after 6 months. For children 0-4 years of age, the effectiveness of primary vaccination against infection, compared with being unvaccinated, was 63·8% (57·0-69·5) at 2 months and 58·1% (48·3-66·1) at 5 months after the first dose, and the effectiveness of omicron infection against reinfection was 77·3% (75·9-78·6) after 3 months and 64·7% (63·3-66·1) after 6 months. For both age groups, vaccination and previous infection had better effectiveness against severe illness as measured by hospital admission or death as a composite endpoint than against infection.

INTERPRETATION

The BNT162b2 and mRNA-1273 vaccines were effective against omicron infection and severe outcomes in children younger than 12 years, although the effectiveness decreased over time. Bivalent boosters were more effective than monovalent boosters. Immunity acquired via omicron infection was high and waned gradually over time. These findings can be used to develop effective prevention strategies against COVID-19 in children younger than 12 years.

FUNDING

US National Institutes of Health.

Characteristics and management of patients with SARS-CoV2 infection admitted to pediatric intensive care units: Data analysis of the Spanish national multicenter registry

INTRODUCTION

The purpose of this study is to describe the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV2) disease characteristics and management in children admitted to the pediatric intensive care units (PICU).

METHODS

The present study was based on a national multicentric prospective registry including PICU patients with SARS-CoV2 infection or symptoms of multisystem inflammatory syndrome in children (MIS-C).

RESULTS

A total of 298 patients were admitted to 41 different Spanish PICUs. A total of 76% of them were previously healthy. The most frequent manifestation was MIS-C (69.8%). On admission, 59.4% of patients did not have respiratory distress, and only 17.4% needed conventional mechanical ventilation (MV). The need for MV was associated with age (incidence rate ratios [IRR] 1.21, p < .012), pediatric sequential organ failure assessment score (p-SOFA) Score (IRR 1.12, p = .001), and need for transfusion (IRR 4.5, p < .004) in MIS-C patients, and with vasoactive drug use (IRR 2.73, p = .022) and the diagnosis of acute respiratory distress syndrome (IRR 2.83, p = .018) in patients admitted for other reasons. During the first day of admission, 56% of patients met shock criteria and 50.7% needed vasoactive drugs. In MIS-C patients, their use was associated with higher p-SOFA score (IRR 1.06, p < .001) and with the diagnosis of shock (IRR 5.78, p < .001). In patients without MIS-C, it was associated with higher p-SOFA score (IRR 1.05, p = .022). The mortality rate was 3%, being lower in MIS-C patients compared to patients admitted for other reasons (0.5% vs. 9.4%, p < .001). It was also lower in previously healthy patients compared to patients with previous comorbidities (0.9% vs. 9.7%, p < .001).

CONCLUSIONS

Severe SARS-CoV2 infection is uncommon in the pediatric population. In our series, respiratory distress was rare, being MIS-C the most frequent cause of PICU admission related to SARS-CoV2. In most cases, the course of the disease was mild except in children with previous diseases.

mRNA vaccines against respiratory viruses

PURPOSE OF REVIEW

The successes of the coronavirus disease 2019 (COVID-19) mRNA vaccines have accelerated the development of mRNA vaccines against other respiratory pathogens. The aim of this review is to highlight COVID-19 mRNA vaccine advances and provide an update on the progress of mRNA vaccine development against other respiratory pathogens.

RECENT FINDINGS

The COVID-19 mRNA vaccines demonstrated effectiveness in preventing severe COVID-19 and death. H7N9 and H10N8 avian influenza mRNA vaccines have demonstrated safety and immunogenicity in phase 1 clinical trials. Numerous seasonal influenza mRNA vaccines are in phase 1-3 clinical trials. Respiratory syncytial virus (RSV) mRNA vaccines have progressed to phase 2-3 clinical trials in adults and a phase 1 clinical trial in children. A combined human metapneumovirus and parainfluenza-3 mRNA vaccines was found to be well tolerated and immunogenic in a phase 1 trial among adults and trials are being conducted among children. Clinical trials of mRNA vaccines combining antigens from multiple respiratory viruses are underway.

SUMMARY

The development of mRNA vaccines against respiratory viruses has progressed rapidly in recent years. Promising vaccine candidates are moving through the clinical development pathway to test their efficacy in preventing disease against respiratory viral pathogens.

Different Safety Pattern of an Inactivated SARS-CoV-2 Vaccine (CoronaVac®) According to Age Group in a Pediatric Population from 3 to 17 Years Old, in an Open-Label Study in Chile

During the COVID-19 pandemic, the importance of vaccinating children against SARS-CoV-2 was rapidly established. This study describes the safety of CoronaVac® in children and adolescents between 3- and 17-years-old in a multicenter study in Chile with two vaccine doses in a 4-week interval. For all participants, immediate adverse events (AEs), serious AEs (SAEs), and AEs of special interest (AESIs) were registered throughout the study. In the safety subgroup, AEs were recorded 28 days after each dose. COVID-19 surveillance was performed throughout the study. A total of 1139 individuals received the first and 1102 the second dose of CoronaVac®; 835 were in the safety subgroup. The first dose showed the highest number of AEs: up to 22.2% of participants reported any local and 17.1% systemic AE. AEs were more frequent in adolescents after the first dose, were transient, and mainly mild. Pain at the inoculation site was the most frequent AE for all ages. Fever was the most frequent systemic AE for 3-5 years old and headache in 6-17 years old. No SAEs or AESIs related to vaccination occurred. Most of the COVID-19 cases were mild and managed as outpatients. CoronaVac® was safe and well tolerated in children and adolescents, with different safety patterns according to age.

Immunogenicity and reactogenicity of fractional, heterologous primary COVID-19 vaccination schedules with BNT162b2 boosters in 5-11-year-old Thai children: A multicenter, prospective, double-blind, randomized control trial

OBJECTIVE

To evaluate immunogenicity and safety of heterologous COVID-19 primary vaccination regimens of CoronaVac with fractional and standard BNT162b2 dosages in 5-11-year-old Thai children.

METHODS

This prospective, multicenter, double-blind, randomized control trial divided participants 1:1:1:1 to receive a second dose of either standard (10-μg) or half-dose (5-μg) BNT162b2 vaccines as follows: CoronaVac/10-μg-BNT162b2 (Group 1), CoronaVac/5-μg-BNT162b2 (Group 2), 10-μg-BNT162b2/10-μg-BNT162b2 (Group 3), or 10-μg-BNT162b2/5-μg-BNT162b2 (Group 4). A subset of participants from each arm received 10-μg-BNT162b2 booster (third) doses 16 weeks after their second vaccination. Humoral and cellular immunogenicity were assessed and adverse events (AEs) digitally self-reported.

RESULTS

Of 553 enrolled participants, 50 % were male, the median (interquartile range) age was 8.65 (7.00, 10.00) years, and a majority (91 %) had normal weight-for-height. All participants exhibited similarly robust neutralizing antibodies (NAb) against the ancestral Wuhan strain two weeks after the second vaccination, with titers highest in Group 1 (737.60, 95% CI [654.80, 830.88]), followed by Groups 3 (630.42, 95% CI [555.50, 715.45]), 2 (593.98, 95% CI [506.02, 697.23]), and 4 (451.79, 95% CI [388.62, 525.23]), as well as 56.01 % and 49.68 % seroconversion for BA.1 and BA.5, respectively. Half-dose BNT162b2 as a second dose induced significantly lower NAb titers compared to their respective full-dose regimens (p = 0.03 for Groups 1 vs 2 and p < 0.001 for Groups 3 vs 4). 77.71 % of participants developed SARS-CoV-2 ancestral spike protein-specific T-cell responses two weeks after the second vaccination. This was similar across arms. Booster doses generated NAb titers 5.69-11.51-folds higher than the second vaccination against BA.1. AEs were similar across arms, all mild or moderate, and fully resolved 2-3 days thereafter.

CONCLUSION

Standard and fractional heterologous regimens of CoronaVac-BNT162b2 induced similar or higher humoral immunity than homologous BNT162b2 and represent alternative vaccine regimens for children. These findings are highly relevant in settings concurrently using both vaccines.

Risk of SARS-CoV-2 Infection Among Households With Children in France, 2020-2022

Importance

Understanding the contribution of children to SARS-CoV-2 circulation in households is critical for designing public health policies and mitigation strategies.

Objective

To identify temporal changes in the risk of SARS-CoV-2 infection in people living with children.

Design, Setting, and Participants

This case-control study included online questionnaire responses from French adults between October 2020 and October 2022. Eligible cases were adults with ongoing SARS-CoV-2 infection with an email address on record with the national health insurance system, which centralized all new diagnoses in France. Eligible controls were adults who had never tested positive for SARS-CoV-2 until February 2021, when eligibility was extended to all adults without ongoing SARS-CoV-2 infection.

Exposure

Transmission of SARS-CoV-2 from a child (aged under 18 years) within the household in the descriptive analysis, as reported by the participating case. Sharing household with a child (of any age or broken down by school level) in the case-control analysis.

Main Outcome and Measures

Ongoing SARS-CoV-2 infection diagnosed by reverse transcription-polymerase chain reaction or supervised rapid antigen test (ie, not self-tests).

Results

A total of 682 952 cases were included for the descriptive analysis (68.8% female, median [IQR] age, 44 [34-55] years). Among those, 45 108 (6.6%) identified a household child as the source case; this proportion peaked at 10.4% during the Omicron BA.1 wave (December 20, 2021, to April 8, 2022). For the case-control analysis, we matched 175 688 cases (with a 4:1 ratio) for demographic characteristics with 43 922 controls. In multivariable logistic regression analysis, household exposure to children was associated with an increased risk of infection mainly at the end of summer 2021 (receding Delta wave) and during winter 2022 (Omicron BA.1 wave). In subgroup analysis by school level of the child, living with children under the age of 6 was associated with increased odds of infection throughout the study period, peaking at an odds ratio (OR) 1.8 (95% CI, 1.6-2.1) for children looked after by professional in-home caregivers, 1.7 (95% CI, 1.5-1.7) for children in day care facilities, and 1.6 (95% CI, 1.4-1.8) for children in preschool. The ORs associated with household exposure to children aged 6 to 14 years increased during the Delta (August 14, 2021, to December 19, 2021) and Omicron BA.1 waves, reaching 1.6 (95% CI, 1.5-1.7) for primary school children and 1.4 (95% CI, 1.3-1.5) for middle school children. Exposure to older children aged 15 to 17 years was associated with a moderate risk until April 2021, with an OR of 1.2 (95% CI, 1.2-1.3) during curfew in early 2021 (December 4, 2020, to April 8, 2021).

Conclusions and Relevance

The presence of children, notably very young ones, was associated with an increased risk of SARS-CoV-2 infection in other household members, especially during the Delta and Omicron BA.1 waves. These results should help to guide policies targeting children and immunocompromised members of their household.

Dilemmas and options for COVID-19 vaccination in children

Over 16 million children have been detected positive for the coronavirus disease 2019 (COVID-19) in the United States since the outbreak of the pandemic. In general, children infected with severe acute respiratory syndrome coronavirus type 2 tend to have lighter symptoms than adults. However, in some cases, the infection can develop into severe forms, such as multisystem inflammatory syndrome in children. Moreover, long-term public health preventive interventions have had some negative effects on the physical and mental health of children. Given the important role that vaccination plays in reducing severe illness and mortality, it is essential for the efficient implementation of vaccination in the pediatric population. Nevertheless, parental distrust of vaccination, especially with regard to its safety and efficacy, hinders this process. Herein, we comprehensively summarize the available data on the safety and effectiveness of COVID-19 vaccine in children. The results show that the currently approved COVID-19 vaccine is safe and effective for children. Although two doses of vaccine in children seem insufficient to prevent Omicron infection, the booster dose provides enhanced protection against infection and severe illness. Most importantly, the bivalent vaccine has been approved for use in the pediatric population to extend the immune response to currently circulating Omicron variant. And the immune protection afforded to newborns after maternal vaccination appears to last only 6 months. Therefore, in the current situation where the rate of virus mutation is accelerating and the COVID-19 pandemic is still severe, it is crucial to extend vaccine protection to children over 6 months of age to weave a tighter safety net.

Effectiveness of Monovalent and Bivalent mRNA Vaccines in Preventing COVID-19-Associated Emergency Department and Urgent Care Encounters Among Children Aged 6 Months-5 Years - VISION Network, United States, July 2022-June 2023

On June 19, 2022, the original monovalent mRNA COVID-19 vaccines were approved as a primary series for children aged 6 months-4 years (Pfizer-BioNTech) and 6 months-5 years (Moderna) based on safety, immunobridging, and limited efficacy data from clinical trials. On December 9, 2022, CDC expanded recommendations for use of updated bivalent vaccines to children aged ≥6 months. mRNA COVID-19 vaccine effectiveness (VE) against emergency department or urgent care (ED/UC) encounters was evaluated within the VISION Network during July 4, 2022-June 17, 2023, among children with COVID-19-like illness aged 6 months-5 years. Among children aged 6 months-5 years who received molecular SARS-CoV-2 testing during August 1, 2022-June 17, 2023, VE of 2 monovalent Moderna doses against ED/UC encounters was 29% (95% CI = 12%-42%) ≥14 days after dose 2 (median = 100 days after dose 2; IQR = 63-155 days). Among children aged 6 months-4 years with a COVID-19-like illness who received molecular testing during September 19, 2022-June 17, 2023, VE of 3 monovalent Pfizer-BioNTech doses was 43% (95% CI = 17%-61%) ≥14 days after dose 3 (median = 75 days after dose 3; IQR = 40-139 days). Effectiveness of ≥1 bivalent dose, comparing children with at least a complete primary series and ≥1 bivalent dose to unvaccinated children, irrespective of vaccine manufacturer, was 80% (95% CI = 42%-96%) among children aged 6 months-5 years a median of 58 days (IQR = 32-83 days) after the dose. All children should stay up to date with recommended COVID-19 vaccines, including initiation of COVID-19 vaccination immediately when they are eligible.

Mpox virus mRNA-lipid nanoparticle vaccine candidates evoke antibody responses and drive protection against the Vaccinia virus challenge in mice

In response to the human Mpox (hMPX) epidemic that began in 2022, there is an urgent need for a monkeypox vaccine. Here, we have developed a series of mRNA-lipid nanoparticle (mRNA-LNP)-based vaccine candidates that encode a collection of four highly conserved Mpox virus (MPXV) surface proteins involved in virus attachment, entry, and transmission, namely A29L, A35R, B6R, and M1R, which are homologs to Vaccinia virus (VACV) A27, A33, B5, and L1, respectively. Despite possible differences in immunogenicity among the four antigenic mRNA-LNPs, administering these antigenic mRNA-LNPs individually (5 μg each) or an average mixture of these mRNA-LNPs at a low dose (0.5 μg each) twice elicited MPXV-specific IgG antibodies and potent VACV-specific neutralizing antibodies. Furthermore, two doses of 5 μg of A27, B5, and L1 mRNA-LNPs or a 2 μg average mixture of the four antigenic mRNA-LNPs protected mice against weight loss and death after the VACV challenge. Overall, our data suggest that these antigenic mRNA-LNP vaccine candidates are both safe and efficacious against MPXV, as well as diseases caused by other orthopoxviruses.

Safety and Immunogenicity of SARS-CoV-2 Recombinant Spike Protein Vaccine in Children and Adolescents in India: A Phase 2-3 Randomized Clinical Trial

Importance

The recombinant COVID-19 vaccine NVX-CoV2373 has demonstrated efficacy of approximately 90% in adults; however, its safety and efficacy in children is unknown.

Objective

To assess the noninferiority of SII-NVX-CoV2373 in children and adolescents compared to adults and to evaluate its safety in comparison with placebo.

Design, Setting, and Participants

This phase 2-3 observer-blind randomized clinical trial was conducted in 2 cohorts, children (aged 2 to 11 years) and adolescents (aged 12 to 17 years) between August 2021 and August 2022. Participants were randomized 3:1 to SII-NVX-CoV2373 or placebo and monitored for 179 days. The participants, study team, and laboratory staff were blinded. This was a multicenter study conducted across 10 tertiary care hospitals in India. Exclusion criteria included previous COVID-19 infection or vaccination, immunocompromised condition, and immunosuppressive medications.

Interventions

Two doses of 0.5-mL SII-NVX-CoV2373 or placebo were administered intramuscularly on days 1 and 22.

Main Outcomes and Measures

Primary outcomes were geometric mean titer ratio of both anti-spike (anti-S) IgG and neutralizing antibodies (NAbs) between both pediatric age groups to that of adults on day 36. Noninferiority was concluded if the lower bound of 95% CI of this ratio was greater than 0.67 for each age group. Both the antibodies were assessed for the index strain and for selected variants at various time points. Solicited adverse events (AEs) were recorded for 7 days after each vaccination, unsolicited AEs were recorded for 35 days, and serious AEs and AEs of special interest were recorded for 179 days.

Results

A total of 460 children in each age cohort were randomized to receive vaccine or placebo. The mean (SD) age was 6.7 (2.7) years in the child cohort and 14.3 (1.6) years in the adolescent cohort; 231 participants (50.2%) in the child cohort and 218 in the adolescent cohort (47.4%) were female. Both anti-S IgG and NAb titers were markedly higher in the SII-NVX-CoV2373 group than in the placebo group on both day 36 and day 180. The geometric mean titer ratios compared to those in adults were 1.20 (95% CI, 1.08-1.34) and 1.52 (95% CI, 1.38-1.67) for anti-S IgG in adolescents and children, respectively; while for NAbs, they were 1.33 (95% CI, 1.17-1.50) and 1.93 (95% CI, 1.70-2.18) in adolescents and children, respectively, indicating noninferiority. SII-NVX-CoV2373 also showed immune responses against variants studied. Injection site reactions, fever, headache, malaise, and fatigue were common solicited AEs. There were no AEs of special interest and no causally related serious AEs.

Conclusions and Relevance

SII-NVX-CoV2373 was safe and well tolerated in children and adolescents in this study. The vaccine was highly immunogenic and may be used in pediatric vaccination against COVID-19.

Trial Registration

Clinical Trials Registry of India Identifier: CTRI/2021/02/031554.

CASCADIA: a prospective community-based study protocol for assessing SARS-CoV-2 vaccine effectiveness in children and adults using a remote nasal swab collection and web-based survey design

INTRODUCTION

Although SARS-CoV-2 vaccines were first approved under Emergency Use Authorization by the Food and Drug Administration in late 2020 for adults, authorisation for young children 6 months to <5 years of age did not occur until 2022. These authorisations were based on clinical trials, understanding real-world vaccine effectiveness (VE) in the setting of emerging variants is critical. The primary goal of this study is to evaluate SARS-CoV-2 VE against infection among children aged >6 months and adults aged <50 years.

METHODS

CASCADIA is a 4-year community-based prospective study of SARS-CoV-2 VE among 3500 adults and paediatric populations aged 6 months to 49 years in Oregon and Washington, USA. At enrolment and regular intervals, participants complete a sociodemographic questionnaire. Individuals provide a blood sample at enrolment and annually thereafter, with optional blood draws every 6 months and after infection and vaccination. Participants complete weekly self-collection of anterior nasal swabs and symptom questionnaires. Swabs are tested for SARS-CoV-2 and other respiratory pathogens by reverse transcription-PCR, with results of selected pathogens returned to participants; nasal swabs with SARS-CoV-2 detected will undergo whole genome sequencing. Participants who test positive for SARS-CoV-2 undergo serial swab collection every 3 days for 21 days. Serum samples are tested for SARS-CoV-2 antibody by binding and neutralisation assays.

ANALYSIS

The primary outcome is SARS-CoV-2 infection. Cox regression models will be used to estimate the incidence rate ratio associated with SARS-CoV-2 vaccination among the paediatric and adult population, controlling for demographic factors and other potential confounders.

ETHICS AND DISSEMINATION

All study materials including the protocol, consent forms, data collection instruments, participant communication and recruitment materials, were approved by the Kaiser Permanente Interregional Institutional Review Board, the IRB of record for the study. Results will be disseminated through peer-reviewed publications, presentations, participant newsletters and appropriate general news media.

Considerations for vaccinating children against COVID-19

COVID-19 vaccines have been introduced in children and adolescents in many countries. However, high levels of community transmission and infection-derived immunity make the decision to introduce COVID-19 vaccination of children in countries yet to do so particularly challenging. For example, other vaccine preventable diseases, including measles and polio, generally have far higher childhood morbidity and mortality in low-income and middle-income countries (LMICs) than COVID-19, and coverage with these vaccines has declined during the pandemic. Many countries are yet to introduce pneumococcal conjugate and rotavirus vaccines for children, which prevent common causes of childhood death, or human papillomavirus vaccine for adolescents. The Pfizer and Moderna COVID-19 vaccines that have been widely tested in children and adolescents have a positive risk-benefit profile. However, the benefit is less compared with other life-saving vaccines in this age group, particularly in LMICs and settings with widespread infection-derived immunity. The resources required for rollout may also pose a considerable challenge in LMICs. In this paper, we describe COVID-19 in children, with a focus on LMICs, and summarise the published literature on safety, efficacy and effectiveness of COVID-19 vaccination in children and adolescents. We highlight the complexity of decision-making regarding COVID-19 vaccination of children now that most of this low-risk population benefit from infection-derived immunity. We emphasise that at-risk groups should be prioritised for COVID-19 vaccination; and that if COVID-19 vaccines are introduced for children, the opportunity should be taken to improve coverage of routine childhood vaccines and preventative healthcare. Additionally, we highlight the paucity of epidemiological data in LMICs, and that for future epidemics, measures need to be taken to ensure equitable access to safe and efficacious vaccines before exposure to infection.

Impact of congenital heart disease on outcomes among pediatric patients hospitalized for COVID-19 infection

BACKGROUND

COVID-19 infection is generally regarded as an acute self-limiting illness in children, but it can cause significant morbidity and mortality in both healthy and high-risk children. There are limited data on the outcomes of children with congenital heart disease (CHD) and COVID-19. This study aimed to examine the risks of mortality, in-hospital cardiovascular and non-cardiovascular complications in this patient population.

METHODS

We analyzed data from hospitalized pediatric patients from 2020 using the nationally representative National Inpatient Sample (NIS). Children hospitalized for COVID-19 were included, and weighted data were used to compare in-hospital mortality and morbidities between children with and without CHD.

RESULTS

Out of 36,690 children admitted with a diagnosis of COVID-19 infection(ICD-10 code:U07.1 and B97.29) during calendar year 2020, 1240 (3.4%) had CHD. The risk of mortality in children with CHD was not significantly higher than those without CHD(1.2% vs. 0.8%, p = 0.50), with adjusted OR (aOR) of 1.7 (95% CI: 0.6-5.3). Tachyarrhythmias and heart block were more likely in CHD children with an aOR of 4.2 (95% CI: 1.8-9.9) and aOR of 5.0 (95% CI: 2.4-10.8), respectively. Similarly, respiratory failure [aOR = 2.0 (1.5-2.8)], respiratory failure requiring non-invasive mechanical ventilation [aOR = 2.7 (1.4-5.2)] and invasive mechanical ventilation [aOR = 2.6 (1.6-4.0)], and acute kidney injury [aOR = 3.4 (2.2-5.4)] were all significantly higher among patients with CHD. Median length of hospital stay in children with CHD was longer than those without CHD [5 days (IQR: 2-11) vs. 3 days (IQR: 2-5), p = < 0.001].

CONCLUSIONS

Children with CHD hospitalized with COVID-19 infection were at increased risk of serious cardiovascular and non-cardiovascular adverse clinical outcomes. They also had increased length of hospital stay and utilization of healthcare resources.

Safety outcomes associated with the Moderna COVID-19 vaccine (mRNA-1273): a literature review

INTRODUCTION

Current safety data from Phase 3 clinical trials have concluded that apart from transient local and systemic reactions, no safety concerns were identified for the Moderna COVID-19 vaccine (mRNA-1273). However, Phase 3 studies are insufficient to detect rare adverse events (AEs), including anaphylactic reactions or myocarditis. A literature search of the two major electronic databases, Embase and Pubmed, was performed to enable the identification and characterization of all relevant articles from December 2020 to November 2022.

AREAS COVERED

This narrative review aims to summarize the key safety outcomes associated with the mRNA-1273 vaccine to inform healthcare decisions and increase public awareness of mRNA-1273 vaccine safety. The primary adverse events (AEs) reported within a diverse population, including children, adolescents, older adults, pregnant women, and cancer patients receiving the mRNA-1273 vaccine, were; localized injection site pain, fatigue, headache, myalgia, and chills. In addition, the mRNA-1273 vaccine was also associated with; less than a 1-day change in the menstrual cycle, a 10-fold higher risk of myocarditis and pericarditis within young males aged 18-29 years and increased levels of anti-polyethylene glycol (PEG) antibodies.

EXPERT OPINION

The transient nature of commonly observed AEs and the rare occurrence of severe events within mRNA-1273 recipients show no significant safety concerns which should prevent vaccination. However, large-scale epidemiological studies with longer follow-up periods are required to surveillance rare safety outcomes associated with this vaccine.

Maternal third dose of BNT162b2 mRNA vaccine and risk of infant COVID-19 hospitalization

Infants are at a higher risk of Coronavirus Disease 2019 (COVID-19)-related hospitalizations compared to older children. In this study, we investigated the effect of the recommended third maternal dose of BNT162b2 COVID-19 vaccine during pregnancy on rates of infant COVID-19-related hospitalizations. We conducted a nationwide cohort study of all live-born infants delivered in Israel between 24 August 2021 and 15 March 2022 to estimate the effectiveness of the third booster dose versus the second dose against infant COVID-19-related hospitalizations. Data were analyzed for the overall study period, and the Delta and Omicron periods were analyzed separately. Cox proportional hazard regression models estimated hazard ratios and 95% confidence intervals (CIs) for infant hospitalizations according to maternal vaccination status at delivery. Among 48,868 live-born infants included in the analysis, rates of COVID-19 hospitalization were 0.4%, 0.6% and 0.7% in the third-dose, second-dose and unvaccinated groups, respectively. Compared to the second dose, the third dose was associated with reduced infant hospitalization with estimated effectiveness of 53% (95% CI: 36-65%). Greater protection was associated with a shorter interval between vaccination and delivery. A third maternal dose during pregnancy reduced the risk of infant hospitalization for COVID-19 during the first 4 months of life, supporting clinical and public health guidance for maternal booster vaccination to prevent infant COVID-19 hospitalization.

COVID-19 Vaccines for Children: An Update

The coronavirus disease 2019 (COVID-19) pandemic has had a large effect on the pediatric population, with 16,000,000 cases and counting. Currently, there are two messenger RNA (mRNA)-based and a single adjuvanted, protein-based COVID-19 vaccine approved for use in children and adolescents in the United States. Multiple studies have highlighted that these vaccines are safe for use in children and adolescents and are effective at reducing COVID-19 infection and complications. Given the risk of the SARS-CoV-2 virus to the pediatric population and ongoing global viral transmission, it is advised that providers emphasize the value of COVID-19 vaccination for children and adolescents. [Pediatr Ann. 2023;52(3):e83-e88.].

Preliminary Estimates of Effectiveness of Monovalent mRNA Vaccines in Preventing Symptomatic SARS-CoV-2 Infection Among Children Aged 3-5 Years - Increasing Community Access to Testing Program, United States, July 2022-February 2023

On June 18, 2022, the Advisory Committee on Immunization Practices (ACIP) issued interim recommendations for use of the 2-dose monovalent Moderna COVID-19 vaccine as a primary series for children aged 6 months-5 years* and the 3-dose monovalent Pfizer-BioNTech COVID-19 vaccine as a primary series for children aged 6 months-4 years,^† based on safety, immunobridging, and limited efficacy data from clinical trials (1-3). Monovalent mRNA vaccine effectiveness (VE) against symptomatic SARS-CoV-2 infection was evaluated using the Increasing Community Access to Testing (ICATT) program, which provides SARS-CoV-2 testing to persons aged ≥3 years at pharmacy and community-based testing sites nationwide^§ (4,5). Among children aged 3-5 years with one or more COVID-19-like illness symptoms^¶ for whom a nucleic acid amplification test (NAAT) was performed during August 1, 2022-February 5, 2023, VE of 2 monovalent Moderna doses (complete primary series) against symptomatic infection was 60% (95% CI = 49% to 68%) 2 weeks-2 months after receipt of the second dose and 36% (95% CI = 15% to 52%) 3-4 months after receipt of the second dose. Among symptomatic children aged 3-4 years with NAATs performed during September 19, 2022-February 5, 2023, VE of 3 monovalent Pfizer-BioNTech doses (complete primary series) against symptomatic infection was 31% (95% CI = 7% to 49%) 2 weeks-4 months after receipt of the third dose; statistical power was not sufficient to estimate VE stratified by time since receipt of the third dose. Complete monovalent Moderna and Pfizer-BioNTech primary series vaccination provides protection for children aged 3-5 and 3-4 years, respectively, against symptomatic infection for at least the first 4 months after vaccination. CDC expanded recommendations for use of updated bivalent vaccines to children aged ≥6 months on December 9, 2022 (6), which might provide increased protection against currently circulating SARS-CoV-2 variants (7,8). Children should stay up to date with recommended COVID-19 vaccines, including completing the primary series; those who are eligible should receive a bivalent vaccine dose.

mRNA vaccines: The future of prevention of viral infections?

Messenger RNA (mRNA) vaccines against COVID-19 are the first authorized biological preparations developed using this platform. During the pandemic, their administration has been proven to be a life-saving intervention. Here, we review the main advantages of using mRNA vaccines, identify further technological challenges to be met during the development of the mRNA platform, and provide an update on the clinical progress on leading mRNA vaccine candidates against different viruses that include influenza viruses, human immunodeficiency virus 1, respiratory syncytial virus, Nipah virus, Zika virus, human cytomegalovirus, and Epstein-Barr virus. The prospects and challenges of manufacturing mRNA vaccines in low-income countries are also discussed. The ongoing interest and research in mRNA technology are likely to overcome some existing challenges for this technology (e.g., related to storage conditions and immunogenicity of some components of lipid nanoparticles) and enhance the portfolio of vaccines against diseases for which classical formulations are already authorized. It may also open novel pathways of protection against infections and their consequences for which no safe and efficient immunization methods are currently available.

COVID-19 Vaccination in Pediatrics: Was It Valuable and Successful?

BACKGROUND

The mass vaccination of children against coronavirus 2019 disease (COVID-19) has been frequently debated. The risk-benefit assessment of COVID-19 vaccination versus infection in children has also been debated.

AIM

This systematic review looked for answers to the question "was the vaccination of our children valuable and successful?".

METHODS

The search strategy of different articles in the literature was based on medical subject headings. Screening and selection were based on inclusion/exclusion criteria.

RESULTS AND DISCUSSION

The search results revealed that the majority of the reported adverse events after COVID-19 vaccination in pediatrics were mild to moderate, with few being severe. Injection site discomfort, fever, headache, cough, lethargy, and muscular aches and pains were the most prevalent side effects. Few clinical studies recorded significant side effects, although the majority of these adverse events had nothing to do with vaccination. In terms of efficacy, COVID-19 disease protection was achieved in 90-95% of cases for mRNA vaccines, in 50-80% of cases for inactivated vaccines, and in 58-92% of cases for adenoviral-based vaccines in children and adolescents.

CONCLUSIONS

Based on available data, COVID-19 immunizations appear to be safe for children and adolescents. Furthermore, multiple studies have proven that different types of vaccines can provide excellent protection against COVID-19 in pediatric populations. The efficacy of vaccines against new SARS-CoV-2 variants and the reduction in vaccine-related long-term adverse events are crucial for risk-benefit and cost-effectiveness assessments; therefore, additional safety studies are required to confirm the long-term safety and effectiveness of vaccinations in children.

COVID-19 Vaccines in Children

The coronavirus disease 2019 (COVID-19) pandemic has transformed the world. It has highlighted health inequities, the lack of social safety nets, and the limitations of health care systems. But it has also paved the way for medical ingenuity and technological advances in the face of these extreme challenges. One such medical marvel is the COVID-19 vaccine. The ability to rapidly create and mass produce a safe and effective vaccine for both adults and children has been essential to minimizing the harm of COVID-19, reducing the burden on hospitals and ushering in some semblance of return to pre-COVID times. Although vaccine hesitancy and long-standing health inequities have limited the number of children who have received the COVID-19 vaccine, the recommended vaccines remain a vital tool in ensuring healthy growth and development of children. [Pediatr Ann. 2023;52(1):e4-e7.].

Analysis of the adverse events following the mRNA-1273 COVID-19 vaccine

OBJECTIVE

This study aims to characterize the adverse events (AEs) following the administration of the mRNA-1273 COVID-19 vaccine from the Vaccine Adverse Event Reporting System (VAERS) data.

METHODS

In this case/non-case analysis, reports between 1 January 2021, and 27 October 2022, were extracted from VAERS. AEs were defined as preferred terms (PTs) by Medical Dictionary for Regulatory Activities (MedDRA) terminology. Disproportionality analyses were conducted to calculate the reporting odds and proportional reporting ratios. The Bayesian approach was used to calculate information component (IC) values and Empirical Bayesian Geometric Mean scores for all the AEs detected.

RESULTS

186 MedDRA PTs compromising 702,495 AEs associated with the mRNA-1273 vaccine were identified. Three statistically significant signals were identified for general and systemic AEs, administration site conditions, and product issues. Cardiac disorders were rarely reported, the most common being; 489 reports for 'myocarditis' (19.44%), 475 for 'acute myocardial infarction' (18.88%), 457 for 'myocardial infarction' (18.16%), 290 for 'bradycardia' (11.53%) and 281 for 'pericarditis' (11.17%).

CONCLUSIONS

The most frequently identified AEs following mRNA-1273 vaccination agree with those listed within the Summary of Product Characteristics. In addition, disproportionality analysis did not find any statistically significant signals for myocarditis or pericarditis.

Safety, Efficacy, and Immunogenicity of Varying Types of COVID-19 Vaccines in Children Younger Than 18 Years: An Update of Systematic Review and Meta-Analysis

Vaccination is one of the most effective measures for children as the epidemic progresses. However, there is a significant research gap in the meta-analysis of the COVID-19 vaccines for children younger than 18 years. This study is a comprehensive review of different COVID-19 vaccines. Published articles were retrieved from PubMed, Embase, and the Cochrane Library. Twelve randomized controlled trials (RCTs) of COVID-19 vaccines were included in the review until 21 October 2022. Most local and systemic adverse reactions were predominantly mild to moderate in severity and disappeared quickly after different types of vaccines. The subunit vaccine had the highest safety. The significant risk was lower in the subunit vaccine group after the initial (RR 1.66, 95% CI 1.26-2.17, p = 0.0003) and booster vaccination (RR 1.40, 95% CI 1.02-1.92, p = 0.04). Younger children had a more outstanding safety profile in the mRNA and inactivated vaccine groups. The humoral immune response was proportional to the number of doses in the inactivated and the adenovirus vaccine groups, and the strength of immunogenicity was negatively correlated with age in the inactivated vaccine. The mRNA and the subunit vaccines provided satisfactory prevention against COVID-19, especially seven days after the booster dose. However, more research and longer-term follow-up are needed to assess the duration of immune responses, efficacy, and safety.

Vaccinating Children against SARS-CoV-2: A Literature Review and Survey of International Experts to Assess Safety, Efficacy and Perceptions of Vaccine Use in Children

Introduction: The balance of risks and benefits of COVID-19 vaccination in children is more complex than in adults with limited paediatric data resulting in no global consensus on whether all healthy children should be vaccinated. We sought to assess the safety, efficacy, and effectiveness of childhood vaccination against SARS-CoV-2, as well as better understanding perceptions of vaccination in parents and vaccine experts. Methods: We performed a literature review for COVID-19 vaccine safety, efficacy, effectiveness, and perceptions. We searched international safety databases for safety data and developed an electronic survey to elicit country-specific COVID-19 immunisation data, including vaccine regulations, policies, rates, and public attitudes solicited from vaccine experts. Results: Nine studies were included in the final safety analysis. Local reactions were frequently reported across all studies and vaccine types. Adverse events reported to surveillance systems tended to be non-serious, and commonly included injection site reactions and dizziness. Twenty-three studies reported immunogenicity, efficacy, and effectiveness data. There were nine randomised control trials of six different vaccine types, which showed seroconversion of neutralising antibodies in vaccinated children ranging from 88% to 100%. The vaccine efficacy for Pfizer and Moderna vaccines ranged from 88% to 100%. There were 118 survey responses representing 55 different countries. Reported vaccination rates ranged from <1% to 98%. Most respondents described “mixed opinions” regarding paediatric vaccination policies in their country. By region, a more positive public attitude towards vaccination correlated with higher vaccination rates. Discussion: In this mixed-methods review, we have found evidence that vaccination against COVID-19 in children is safe, efficacious, and effective. Overall, the combined evidence from both the literature review and survey highlights the need for further data on both the safety and effectiveness of COVID-19 vaccinations in children.