Covid vaccinations in children under 12

Covid and covid vaccinations in children under 12:

With the recent news of covid vaccines being made available to younger children, we have been contacted by a number of parents keen for information to aid their decision making as to whether they should vaccinate their children, and if so, which vaccine they should give. We have collated the most up to date data to help guide you.

Ultimately, this is your choice as a parent and you will need to consider your family’s individual circumstances and weigh these up against the risks, not only of covid infection in your children as we outline below, but potential transmission of the virus to extended family and the risks we know another extended period of home learning may have on their educational, social and emotional development.

What are the risks of Covid infection in children of this age?:

The vast majority of children with covid will be either asymptomatic or have mild/moderate symptoms and recover within 1-2 weeks. Serious adverse outcomes from covid infection in this age group are rare. Estimating these risks is somewhat complicated as with each new variant, the risks and therefore the data changes. For example, evidence in adults suggest that Omicron may result in less severe disease (1-3) but we do not have the evidence yet to confirm whether this is also true for children. Doctors are also likely to be more cautious when caring for younger patients and so data regarding hospitalisations, may not necessarily reflect disease severity in children.

The serious risks include:
1. Death: This is extremely rare with estimates ranging from 0.03-0.08% in under 18 years old (4). The figure for under 12s is likely to be even lower still.

2. Respiratory distress: In one review of 7500 children early on in the pandemic, 2 % had severe pneumonia requiring support with oxygen and 0.7 % had critical disease requiring intensive care (4). 22% of these children had underlying conditions, of which asthma or another chronic lung condition, were the most common. (4)

3. Multisystem inflammatory syndrome in children (MIS-C): This is characterised by inflammation of the heart, lungs, kidneys, brain, skin, eyes, or gastrointestinal organs in children after covid infection and can lead to multi-organ failure. This is rare, occurring in less than 1% of children and seems to be most common in black, Hispanic and South Asian children, and those with a history of asthma (particularly if uncontrolled) and those with obesity.(5) It seems to be least common in Asian children.

4. Myocarditis: This is inflammation of the heart muscle, which can present with anything from mild/asymptomatic disease to severe chest pain, shock, abnormal heart rhythm and sudden death. The most common cause in children is a viral infection, of which covid infection is one. Pre-covid it was very rare, with an estimated rate of 1-2 per 100000 children 6-7. During covid, we have seen that rate increase by about 30% (8). Although the absolute numbers of children with myocarditis after covid infection is still low, the risk attributable to covid is significant.

5. Neurological problems: These are actually quite common in children hospitalised with covid. Hospitalisation for severe illness in children as we have said is low, so the absolute numbers of children with neurological symptoms is lower still and in the majority, these symptoms will be transient. However, in one series (9), 2.5% of hospitalised children had severe neurological disease including fits, stroke, psychosis and brain swelling. 1% of these children still had neurological deficits at discharge from hospital.

6. Long covid: The number of children with persistent symptoms after covid (fatigue, headache, sleep disturbance, muscle and joint pain, respiratory problems, palpitations, and altered sense of smell or taste) is very inconsistent in reports, ranging from 4-66% (10). Being sure these symptoms are due to covid infection and not due to the effects of the pandemic is tricky; in 3 studies that included a control group, there was no difference in the numbers of children with these symptoms whether they had had a prior covid infection or not (10). Nonetheless, covid is likely to result in persistent symptoms in some children.

What about the risks of the vaccines?:

1. Sinovac:
This is a traditional vaccine, as you know, which uses inactivated virus to stimulate an immune response. This is how many vaccines work and your children are likely to have already received similar ones e.g. polio, influenza and pertussis to name but a few. It contains aluminium hydroxide to boost the immune response, which again is present in many vaccines your children are likely to have had e.g. DTP and hepatitis

Available safety data is taken from phase 1-2 trials (11) (which look at safety, side effects and dosing) and included 550 children. The children were followed up for 28 days. Adverse reactions in that time period were minor, with only 1 serious adverse outcome of pneumonia in 1 child, thought to be unrelated to the vaccine. There were no cases of myocarditis. Nearly all children had detectable antibodies after 2 doses.

As yet, the phase 3 trials are still ongoing and so we do not have any further safety or real-world efficacy data, however, studies have shown the Sinovac vaccine to be effective in preventing hospitalisations and severe disease in adults (12) (albeit slightly less so than the mRNA vaccines), and we would hope that this would be the case in young children.

2. BioNtech:
This uses mRNA technology and seems to be the one to cause most concern amongst parents.

It’s Phase 3 trials (13) have been published and they included 2268 5-11 year old’s, given 2 doses 3 weeks apart, following them up for a few months. The vaccine was safe (no severe effects such as myocarditis or severe allergy were observed), resulted in antibody formation and was 90% effective against covid infection.

We also have the post vaccine reporting (VAERS) data for this age group from October 2021, when the FDA approved the vaccine for this age group. 9 million children have had it in the US since then.

Whilst in the phase 3 trial, there were no cases of myocarditis, there have been reported cases post vaccination in the real world (14) and further studies have confirmed that mRNA vaccines are associated with an increased risk of myocarditis. Most of the additional cases of myocarditis have been in adolescent boys (12-17 years) within 1 week of the 2nd dose of the vaccine (15). In 5-11 year old’s, there have been no extra myocarditis cases in girls but there does seem to be a very small increase in boys of this age after the second dose (14).

The overall risk of getting myocarditis after an mRNA vaccine is still very low, even in adolescent boys, and importantly, your child is less likely to have myocarditis from the vaccine, than they are to have cardiac complications from covid itself.

It’s also important to note that the myocarditis cases we see after vaccination are quite different to typical viral myocarditis cases. After vaccination, the myocarditis is milder, the recovery quicker and severe adverse outcomes such as ICU admission, very rare, unlike with typical viral myocarditis (15,16)

Some parents have been concerned with reports that Hong Kong does not have a license for the paediatric approved BioNTech vaccine. This is not a cause for concern. The paediatric formulation is identical to the adult formulation, save for the dose and so in Hong Kong, a proportion of the adult vaccine is measured and given to children. This is standard practice for vaccines given to children; we do this frequently with other vaccines, such as the adult hepatitis A and B combined vaccine. Both the adult and paediatric formulations are diluted prior to administration during preparation.

More parents still are worried about the lack of long-term data for mRNA vaccines in children. Whilst we see no biologically plausible way that the vaccine can cause long-term harm to your children’s health, as with many things in medicine and life, we cannot give reassurances in absolute terms. We need to remember that whilst complications for covid in children of this age are rare, they are real, and these need to be balanced against unlikely unknowns.

What is happening around the world for vaccinations in this age group?

The UK are currently only vaccinating 5-11 year old’s if they have underlying medical conditions. Here is a link to the green book (17) which lists these conditions. However, this is likely to be extended to include all 5-11 year old’s in the near future.

The USA, Australia, France and Canada are already offering the vaccine to all 5-11 year old’s.

We hope this summary is helpful for those parents who want to understand the current evidence. For more detailed or more specific guidance please make an appointment with your paediatrician or family doctor.


1. Wolter N et al. Early assessment of the clinical severity of the SARS-CoV-2 omicron variant in South Africa: a data linkage study. Lancet 2022

2. Maslo C et al. Characteristics and Outcomes of Hospitalized Patients in South Africa During the COVID-19 Omicron Wave Compared With Previous Waves. JAMA. 2021

3. Abdullah F et al. Decreased severity of disease during the first global omicron variant covid-19 outbreak in a large hospital in tshwane, south africa. Int J Infect Dis. 2021;116:38.

4. Liguoro I et al. SARS-COV-2 infection in children and newborns: a systematic review. Eur J Pediatr. 2020;179(7):1029

5. Feldstein LR et al. Multisystem Inflammatory Syndrome in U.S. Children and Adolescents. N Engl J Med. 2020;383(4):334.

6. Nugent AW et al. The epidemiology of childhood cardiomyopathy in Australia. N Engl J Med. 2003;348

7. Arola A et al. Occurrence and Features of Childhood Myocarditis: A Nationwide Study in Finland. J Am Heart Assoc. 2017;6(11)

8. Boehmer TK, Kompaniyets L, Lavery AM, et al. Association between COVID-19 myocarditis using hospital-based administrative data—United States, March 2020-January 2021. MMWR 2021;70:1128-32

9. LaRovere KL et al. Neurologic Involvement in Children and Adolescents Hospitalized in the United States for COVID-19 or Multisystem Inflammatory Syndrome. JAMA Neurol. 2021;78(5):536

10. Zimmermann P, Pittet LF, Curtis N . How Common is Long COVID in Children and Adolescents? Pediatr Infect Dis J. 2021;40(12):e482

11. Bihua Han et al. Safety, tolerability, and immunogenicity of an inactivated SARS-CoV-2 vaccine (CoronaVac) in healthy children and adolescents: a double-blind, randomised, controlled, phase 1/2 clinical trial. Lancet infect Dis 2021 Dec;21(12):1645-1653

12. Alejandro J et al. Effectiveness of an Inactivated SARS-CoV-2 Vaccine in Chile. N Engl J Med 2021; 385:875-884

13. Emmanuel B et al. Evaluation of the BNT162b2 Covid-19 Vaccine in Children 5 to 11 Years of Age. N Engl J Med 2022; 386:35-46


15. Oster, M et al. Myocarditis Cases Reported After mRNA-Based COVID-19 Vaccination in the US From December 2020 to August 2021. JAMA. 2022;327(4):331-340

16. Tsun Lai FT, Li X, Peng K, Huang L, Ip P, Tong X, Ling Chui CS, Fai Wan EY, Ho Wong CK, Yin Chan EW, Wah Siu DC, Kei Wong IC. Carditis After COVID-19 Vaccination With a Messenger RNA Vaccine and an Inactivated Virus Vaccine : A Case-Control Study. Ann Intern Med. 2022 Jan 25