Assessment of Efficacy and Safety of mRNA COVID-19 Vaccines in Children Aged 5 to 11 Years

Watanabe, Atsuyuki; Kani, Ryoma; Iwagami, Masao; Takagi, Hisato; Yasuhara, Jun; Kuno, Toshiki

doi:10.1001/jamapediatrics.2022.6243

Cited by 51 publications

(40 citation statements)

References 81 publications

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“…Extrapolating this rate to the five to 11 year old population in UK (5 million) and conservatively assuming all would be hospitalised gives a central estimate of 8 hospital admissions due to the vaccine, which we split across UHC and non UHC children 1:7. We note that Watanabe et al report no vaccine-caused deaths among 16.6 million injections [44].…”

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confidence: 51%

“…A systematic review of vaccination for 5-11 year olds reported a myocarditis rate of 1.3-1.8/million vaccinations given [44]. Extrapolating this rate to the five to 11 year old population in UK (5 million) and conservatively assuming all would be hospitalised gives a central estimate of 8 hospital admissions due to the vaccine, which we split across UHC and non UHC children 1:7.…”

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confidence: 99%

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A methodological framework for assessing the benefit of SARS-CoV-2 vaccination following previous infection: case study of five to eleven year olds

Pagel

Wilde

Tomlinson

et al. 2023

Preprint

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Vaccination rates against SARS-CoV-2 in children aged five to 11 years remain low in many countries. The current benefit of vaccination in this age group has been questioned given that the large majority of children have now experienced at least one SARS-CoV-2 infection. However, protection from infection, vaccination or both wanes over time. National decisions on offering vaccines to this age group have tended to be made without considering time since infection. There is an urgent need to evaluate the additional benefits of vaccination in previously infected children and under what circumstances those benefits accrue. We present a novel methodological framework for estimating the potential benefits of COVID-19 vaccination in previously infected children aged five to 11, accounting for waning. We apply this framework to the UK context and for two adverse outcomes: hospitalisation related to SARS-CoV-2 infection and Long Covid. We show that the most important drivers of benefit are: the degree of protection provided by previous infection; the protection provided by vaccination; the time since previous infection; and future attack rates. Vaccination can be very beneficial for previously infected children if future attack rates are high and several months have elapsed since the previous major wave in this group. Benefits are generally larger for Long Covid than hospitalisation, because Long Covid is both more common than hospitalisation and previous infection offers less protection against it. Our framework provides a structure for policy makers to explore the additional benefit of vaccination across a range of adverse outcomes and different parameter assumptions. It can be easily updated as new evidence emerges.

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confidence: 51%

Section: %mentioning

confidence: 99%

A methodological framework for assessing the benefit of SARS-CoV-2 vaccination following previous infection: case study of five to eleven year olds

Pagel

Wilde

Tomlinson

et al. 2023

Preprint

View full text Add to dashboard Cite

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“…The estimated incidence is about 1 in 50 000 across all age groups but as high as 1 in 6600 in people aged 16 to 19 years . The systematic review and meta-analysis by Watanabe et al found that the incidence of myocarditis in children aged 5 to 11 years was about 1 in 500 000. Fortunately, myocarditis following vaccination is generally short-lived and self-resolving …”

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confidence: 99%

“…In this issue of JAMA Pediatrics , Watanabe and coauthors evaluated the safety and efficacy of 2 doses of Pfizer’s messenger RNA (mRNA) vaccine in children aged 5 to 11 years during both the delta and omicron waves of COVID-19. In a systematic review and meta-analysis that included 17 published studies of 10 935 541 vaccinated and 2 635 251 unvaccinated children, they found that the mRNA vaccine was effective at preventing SARS-CoV-2 infection, symptomatic infection, hospitalization, and multisystem inflammatory syndrome in children (MIS-C).…”

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COVID-19 Vaccines in Young Children—Reassuring Evidence for Parents

Offit

2023

JAMA Pediatr

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In this issue of JAMA Pediatrics, Watanabe and coauthors 1 evaluated the safety and efficacy of 2 doses of Pfizer's messenger RNA (mRNA) vaccine in children aged 5 to 11 years during both the delta and omicron waves of COVID-19. In a systematic review and meta-analysis that included 17 published studies of 10 935 541 vaccinated and 2 635 251 unvaccinated children, they found that the mRNA vaccine was effective at preventing SARS-CoV-2 infection, symptomatic infection, hospitalization, and multisystem inflammatory syndrome in children (MIS-C). The vaccine was also safe; myocarditis occurred in only 1.8 per million vaccinees. This analysis offers 2 important advances over previous, smaller studies. First, during both the delta and omicron waves, mRNA vaccines consistently protected against serious illness, including MIS-C. Second, the risk of myocarditis was minuscule.More than 1 year ago, on October 26, 2021, researchers from Pfizer presented results of a prospective, placebo-controlled, phase 3 trial of their mRNA vaccine in 5-to 11-year-old children to the US Food and Drug Administration (FDA) Vaccine and Related Biological Products Advisory Committee. 2 About 1500 children were inoculated with 2 doses of 10 μg of mRNA vaccine administered 3 weeks apart; 750 were inoculated with placebo. At least 1 week after the second dose, 16 cases of symptomatic COVID-19 occurred in the placebo group and 3 in the vaccine group for a calculated efficacy of 90.9% (95% CI, 68.3%-98.3%). Although the FDA later authorized the use of Pfizer's mRNA vaccine for young children, several questions remained unanswered. Because Pfizer's phase 3 study was small, no cases of serious illness or MIS-C were included. Also, whereas those 12 years and older had received 30 ug of Pfizer's mRNA vaccine per dose, children aged 5 to 11 years would now be receiving 10 μg, one-third the dose with which we had had the most experience.One week later, on November 2, 2021, the US Centers for Disease Control and Prevention recommended Pfizer's mRNA vaccine for all 5-to 11-year-old children. Two months later, the omicron variant entered the US. Because omicron contained 15 sequence variations in the receptor-binding domain of the spike protein, it evaded recognition by neutralizing antibodies. Would protection against severe disease, which is the only reasonable and attainable goal of this vaccine, hold up when millions of 5-to 11-year-old children were vaccinated?Between November 2021 and March 2022, 2 studies evaluated the efficacy of 2 doses of Pfizer's mRNA vaccine in children aged 5 to 11 years. 3,4 The numbers of children studied ranged from 1000 to 9000, and confidence intervals were large. Researchers found that protective efficacy against asymptomatic

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COVID-19 Vaccination and Incidence of Pediatric SARS-CoV-2 Infection and Hospitalization

Head,

Collender,

León

et al. 2024

JAMA Netw Open

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ImportanceA SARS-CoV-2 vaccine was approved for adolescents aged 12 to 15 years on May 10, 2021, with approval for younger age groups following thereafter. The population level impact of the pediatric COVID-19 vaccination program has not yet been established.ObjectiveTo identify whether California's pediatric COVID-19 immunization program was associated with changes in pediatric COVID-19 incidence and hospitalizations.Design, Setting, and ParticipantsA case series on COVID-19 vaccination including children aged 6 months to 15 years was conducted in California. Data were obtained on COVID-19 cases in California between April 1, 2020, and February 27, 2023.ExposurePostvaccination evaluation periods spanned 141 days (June 10 to October 29, 2021) for adolescents aged 12 to 15 years, 199 days (November 29, 2021, to June 17, 2022) for children aged 5 to 11 years, and 225 days (July 17, 2022, to February 27, 2023) for those aged 6 to 59 months. During these periods, statewide vaccine coverage reached 53.5% among adolescents aged 12 to 15 years, 34.8% among children aged 5 to 11 years, and 7.9% among those aged 6 to 59 months.Main Outcomes and MeasuresAge-stepped implementation of COVID-19 vaccination was used to compare observed county-level incidence and hospitalization rates during periods when each age group became vaccine eligible to counterfactual rates predicted from observations among other age groups. COVID-19 case and hospitalization data were obtained from the California reportable disease surveillance system.ResultsBetween April 1, 2020, and February 27, 2023, a total of 3 913 063 pediatric COVID-19 cases and 12 740 hospitalizations were reported in California. Reductions of 146 210 cases (95% prediction interval [PI], 136 056-158 948) were estimated among adolescents aged 12 to 15 years, corresponding to a 37.1% (35.5%-39.1%) reduction from counterfactual predictions. Reductions of 230 134 (200 170-265 149) cases were estimated among children aged 5 to 11 years, corresponding to a 23.7% (20.6%-27.3%) reduction from counterfactual predictions. No evidence of reductions in COVID-19 cases statewide were found among children aged 6 to 59 months (estimated averted cases, −259; 95% PI, −1938 to 1019), although low transmission during the evaluation period may have limited the ability to do so. An estimated 168 hospitalizations (95% PI, 42-324) were averted among children aged 6 to 59 months, corresponding to a 24.4% (95% PI, 6.1%-47.1%) reduction. In meta-analyses, county-level vaccination coverage was associated with averted cases for all age groups. Despite low vaccination coverage, pediatric COVID-19 immunization in California averted 376 085 (95% PI, 348 355-417 328) reported cases and 273 (95% PI, 77-605) hospitalizations among children aged 6 months to 15 years over approximately 4 to 7 months following vaccination availability.Conclusions and RelevanceThe findings of this case series analysis of 3 913 063 cases suggest reduced pediatric SARS-CoV-2 transmission following immunization. These results support the use of COVID-19 vaccines to reduce COVID-19 incidence and hospitalization in pediatric populations.

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Assessment of Efficacy and Safety of mRNA COVID-19 Vaccines in Children Aged 5 to 11 Years

Cited by 51 publications

References 81 publications

A methodological framework for assessing the benefit of SARS-CoV-2 vaccination following previous infection: case study of five to eleven year olds

A methodological framework for assessing the benefit of SARS-CoV-2 vaccination following previous infection: case study of five to eleven year olds

COVID-19 Vaccines in Young Children—Reassuring Evidence for Parents

COVID-19 Vaccination and Incidence of Pediatric SARS-CoV-2 Infection and Hospitalization

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