Independent report

COVID-19 vaccination of children aged 6 months to 4 years: JCVI advice, 9 December 2022 (updated 26 April 2023)

Updated 3 May 2023

Introduction

On 31 October and 1 November 2022, the Joint Committee on Vaccination and Immunisation (JCVI) met to review recent data related to COVID-19 paediatric vaccine trials, post-marketing safety surveillance of paediatric COVID-19 vaccines in the United States, and the epidemiology of COVID-19 in the UK in people aged 6 months to 4 years.

JCVI has previously offered advice regarding the vaccination of individuals aged 5 years and older. When formulating advice in relation to childhood immunisations, JCVI has consistently maintained that the focus should be on the potential benefits and harms of vaccination to children and young people themselves, with prevention of severe COVID-19 (hospitalisations and deaths) in children and young people the primary aim.

Advice

Regarding children aged 6 months to 4 years, JCVI advises that:

• children aged 6 months to 4 years in a clinical risk group (as defined in the Green Book) should be offered two 3-microgram doses of the Pfizer-BioNTech COVID-19 vaccine (Comirnaty®) with an interval of at least 8 weeks between the first and second doses

• further advice regarding a potential third 3-microgram dose of the Pfizer-BioNTech COVID-19 vaccine will be issued in due course; for children who are immunosuppressed and are eligible for a third primary dose, please refer to the Green Book for more details

• JCVI does not currently advise COVID-19 vaccination of children aged 6 months to 4 years who are not in a clinical risk group

Considerations

Throughout the COVID-19 pandemic, studies have shown that children are much less likely to develop severe COVID-19 disease than older adults (references 1 and 2). For the vast majority of children, SARS-CoV-2 infection is associated with no, or mild, symptoms. For a smaller proportion of children with pre-existing health conditions, the risk of severe illness is greater (references 3 and 4). The odds of admission to paediatric intensive care units (PICUs) with severe COVID-19 is over 7-fold greater for infants and young children with underlying medical conditions compared to those without underlying medical conditions (Ward, unpublished data).

By September 2022, an estimated 93% of children aged 1 to 4 years had had prior SARS-CoV-2 infection (unpublished, UK Health Security Agency (UKHSA)). Admission rates to hospital and to PICUs for confirmed COVID-19 illness have remained low among children aged 4 years and under. For children aged under one year, it is recognised that clinical assessment of fever from any cause, including mild COVID-19 infection, can be challenging. This is reflected in lower thresholds for hospital referral for very young children compared to older persons (references 5 and 6). Accordingly, hospital admission is considered to be less well correlated with severity of COVID-19 illness in children aged under one year, compared to older persons.

Vaccine safety

Over 1 million COVID-19 vaccine doses (either Pfizer-BioNTech or Moderna vaccines) have been administered to children aged 6 months to 5 years in the United States of America (US) since June 2022 (reference 7). Post-marketing surveillance in this population indicates that the most commonly reported adverse events are local and systemic reactions. There have been no new or unexpected concerns.

Data from the US indicates that the most frequent adverse reactions in children aged 6 months to 2 years were irritability (or crying), sleepiness and fever. Less than 1% of reports of irritability (or crying) or sleepiness were severe. In children aged 3 to 4 years the most frequent adverse reactions were injection site pain, fatigue and fever. Severe fever was reported by 1 to 2% of parents of children aged 6 months to 4 years after doses 1 and 2 of the Pfizer-BioNTech vaccine (reference 8).

Myocarditis is an extremely rare adverse event that has been associated with mRNA COVID-19 vaccines. Amongst children, the risk of myocarditis following vaccination decreases with decreasing age. No myocarditis events were reported to the US Vaccine Adverse Event Reporting System after vaccination of over 1 million children aged 6 months to 4 years (reference 8).

Vaccine efficacy

There is limited data from clinical trials regarding vaccine efficacy against severe COVID-19 in persons aged 6 months to 4 years due to the relative infrequency of severe COVID-19 in this age group. In combined analyses from clinical trials performed by Pfizer-BioNTech, the preliminary, descriptive vaccine efficacy against COVID-19 was 73.2% (95% CI: 43.8% to 87.6%) after dose 3 in persons aged 6 months to 4 years, at a time when Omicron variants were the dominant circulating strains (reference 9). Further trial data continues to accrue.

Based on estimates by UKHSA, in the Omicron era approximately 65,000 children aged 1 to 4 years (regardless of underlying medical conditions) would need to be vaccinated with 2 doses to prevent one person requiring admission to hospital and requiring oxygen, assisted ventilation or admission to PICU. As severe COVID-19 occurs predominantly amongst children with pre-existing underlying medical conditions, the number needed to vaccinate (NNV) amongst those without underlying medical conditions would be considerably higher, than for those within clinical risk groups.

Vaccine dose

Subgroup analyses, undertaken as part of the Pfizer-BioNTech vaccine trials in children aged 6 months to 4 years, indicated that young children with evidence of prior SARS-CoV-2 infection at their baseline appointment had higher antibody levels before vaccination and at one month after their third dose, compared to those who had no evidence of prior infection at baseline (reference 10). This data is consistent with data from studies performed in persons from older age groups demonstrating that individuals with a history of prior SARS-CoV-2 infection generate stronger immune responses to vaccination than individuals without prior infection (reference 11).

Given the high seroprevalence rate in the UK amongst children aged 6 months to 4 years, it is expected that 2 3-microgram doses of Pfizer-BioNTech vaccine (Comirnaty®) will generate strong immune responses. An interval of 8 to 12 weeks between doses improves the immune response to the second dose (reference 12) and may reduce the risk of myocarditis following vaccination (reference 13), compared with a shorter 3 to 4-week dose interval.

Informed consent

In all instances, the offer of vaccination must be accompanied by appropriate information to enable those with parental responsibility to provide informed consent prior to vaccination. UKHSA produces leaflets for parents on COVID-19 vaccines.

Teams responsible for the implementation and deployment of COVID-19 vaccination for persons aged 6 months to 4 years should be appropriately trained and confident regarding the information relevant to the vaccination of these people.

References

1. Deaths in children and young people in England after SARS-CoV-2 infection during the first pandemic year
2. Which children and young people are at higher risk of severe disease and death after hospitalisation with SARS-CoV-2 infection in children and young people: A systematic review and individual patient meta-analysis
3. Risk factors for PICU admission and death among children and young people hospitalized with COVID-19 and PIMS-TS in England during the first pandemic year
4. SARS-CoV-2 tests, confirmed infections and COVID-19-related hospital admissions in children and young people: birth cohort study
5. Fever in under 5s: assessment and initial management. NICE guideline [NG143]
6. Sepsis: recognition, diagnosis and early management. NICE guideline [NG51]
7. COVID-19 vaccine safety update: primary series in young children and booster doses in older children and adults
8. COVID-19 mRNA vaccine safety among children aged 6 months to 5 years - United States, 18 June 2022 to 21 August 2022
9. Summary of product characteristics Comirnaty 3 micrograms/dose concentrate for ages 6 months to 4 years (maroon cap)
10. Vaccines and related biological products advisory committee meeting. June 15, 2022. FDA briefing document. EUA amendment request for Pfizer-BioNTech COVID-19 vaccine for use in children 6 months through 4 years of age, (PDF 612KB)
11. Protection against symptomatic infection with delta (B.1.617.2) and omicron (B.1.1.529), BA.1 and BA.2 SARS-CoV-2 variants after previous infection and vaccination in adolescents in England, August 2021 to March 2022: a national, observational, test-negative, case-control study
12. Serological responses and vaccine effectiveness for extended COVID-19 vaccine schedules in England
13. Epidemiology of myocarditis and pericarditis following mRNA vaccination by vaccine product, schedule, and interdose interval among adolescents and adults in Ontario, Canada