​KKH paediatric infectious disease specialist, Associate Professor Thoon Koh Cheng and child development specialist, Dr Sylvia Choo, respond to top questions by parents about COVID-19 vaccination in young children:

​Why does my young child need to take the COVID-19 vaccination, when children usually get less severe symptoms than adults? Can’t I wait and vaccinate my child when a more developed vaccine is available?

Assoc Prof Thoon: Data1-5 released by the Ministry of Health from November 2021 to January 2022 show a significant number of children in Singapore have been diagnosed with severe COVID-19 infection. Some children had also developed a condition known as multi-system inflammatory syndrome (MIS-C) after recovering from COVID-19.

The incidence of severe infections and MIS-C add up to close to 130 cases per 100,000 children6, which is quite a large number. We are also seeing large numbers of infections in children around the world; also there are more cases of infections or reinfections in persons who are unvaccinated.

Vaccines continue to be amongst the most effective methods that protect against infections. To protect children against infection, we would encourage them to be vaccinated rather than to wait. Waiting means you are unprotected – the longer you wait, the longer you are unprotected.

The currently-available licensed mRNA vaccine for children in Singapore – Pfizer-BioNTech / Comirnaty – has been administered to more than nine million children in the United States, with a good track record of safety and efficacy.


Will the vaccine affect my child’s DNA or development (e.g. puberty and fertility)?

Assoc Prof Thoon: mRNA vaccines have a very short lifespan in a person’s body. The vaccine presents itself to the immune system, which learns to recognise the traits of the virus and develops a response against it. The mRNA vaccine is then quickly broken down and passed out of the body. It does not have the capability to enter the nucleus of a cell and change a person’s DNA.

Based on the immediate data and our understanding of how mRNA vaccines work, the COVID-19 mRNA vaccine does not impact pubertal development. In adolescents (aged 12 to 19 years) who have received the vaccine, we have not seen any data, overseas or locally, that suggest that the vaccine affects puberty nor fertility.

We also have had adults who have conceived after getting the vaccine, and those who received the vaccine during pregnancy – they were well and delivered their baby.


Are there any health conditions that exclude my child from vaccination (e.g. allergies, seizures)?

Assoc Prof Thoon: For the currently-available licensed mRNA vaccine for children in Singapore – Pfizer-BioNTech / Comirnaty – if your child has a proven, prior allergic reaction or severe allergic reaction to a compound called polyethylene glycol, then they would be advised not to take the mRNA vaccine. Also, if the child develops a severe allergic reaction after taking their first dose of the vaccine, they should not take the second dose of the vaccine.

We have had extensive experience in vaccinating adolescents, older children and adults with various allergies and conditions such as Kawasaki Disease, Brugada Syndrome, G6PD deficiency, etc. So far, the data does not suggest that children with these conditions are at an increased risk of any side effects or reactions from the mRNA vaccine. Most children with allergies to substances, dust mite, peanuts, shellfish, seafood, etc. have also taken the mRNA vaccine successfully without complications.

If you have questions regarding your child’s specific health condition or the optimal timing for vaccination before/after a medical procedure, we would advise that you speak with your child’s healthcare provider.


If my child suffers side effects from other vaccinations, does it mean that they will suffer side effects for the COVID-19 vaccination too?

Assoc Prof Thoon: We have vaccinated many adults and adolescents who have had a history of side effects from other vaccines; thus far, we observed that they have had no significant different reactions beyond what we expected for the COVID-19 mRNA vaccines, as with the general population.

Side effects such as pain, redness and swelling over the injection site, nausea, headache, fever, lethargy are typical and mild, and expected to self-resolve in one to two days. Parents can monitor the child’s temperature, breathing, any signs of rash, swelling, general discomfort, crankiness, and whether the child is using the injected arm normally. Should there be any concerns, please seek medical attention.


Is the vaccine safe for children with special needs?

Dr Choo: While there have been no studies that reported on specific populations of children, the vaccine has been given to more than nine million in the United States, including children with multiple, complex medical conditions and developmental disabilities. Thus far, it has been safe for children with multiple medical conditions and developmental disabilities.


What can I do to prepare my young child for vaccination?

Dr Choo:

  • Choose coping strategies that will suit and help your child based on his/her developmental age and day-to-day behaviour. You know your child best.
  • Be honest about the vaccination. Acknowledge that there may be pain but the discomfort will subside quickly.
  • Consider role-modelling as a method to encourage your child. For instance, share that mummy and daddy have also had this vaccination, and details such as where, when, and what the process was like, etc.
  • For children with high levels of anxiety about vaccination, particularly those with a phobia of needles, refrain from “over talking” and bringing up the topic too often before the appointment. Consider using words other than “injection” when speaking about the matter.
  • For younger children, you can use large visuals to familiarise them with the process, and the “first…then…” approach. For example, tell the child that they will first complete the vaccination, then be rewarded for doing so. Rewards can consist of their favourite activities, items or food, such as taking a ride on a double-decker bus or having an ice-cream after vaccination. You also can immediately reward their child right after vaccination, such as bringing along a band-aid with their favourite cartoon character for their injection site.
  • As the vaccination exercise takes place at the beginning of the school year, newly-enrolled children may not have established familiarity with or attachment to the school yet. To minimise the possibility of your child associating vaccination with school, if possible, consider vaccination at one of the Paediatric National Vaccination Centres, to avoid school avoidance or refusal.
  • Similar to adults and adolescents, children aged five to 11 years are recommended to avoid strenuous activities two weeks after they have received a dose of the vaccine. As part of the preparation leading up to the child’s vaccination, parents can decide together with their child, on light activities that they can engage in during this period of time post-vaccination. These could include the child’s favourite games at home or going to the playground. They should avoid running for a prolonged period of time.


What are the findings of the KKH vaccination trial?

Assoc Prof Thoon: As at January 2022, all 150 participants of the trial had completed two doses of the vaccination. Interim results based on the analysis of 50 participants showed the development of protective antibodies, with a median level of 64.1 per cent about 21 days after receiving the first dose. After the second dose, their protective antibody levels increased significantly to a median level of 96 per cent. These findings are comparable to the safety profile in published reports overseas.

We also observed that the vast majority of the participants experienced minimal side effects. These included typical and mild local side effects such as pain, redness and swelling of the injection site. Some experienced mild systemic effects such as nausea, headache, fever or lethargy. Most participants bounced back within one to two days after the vaccination. There had been no reports of hospitalisation post-vaccination amongst the participants, and they will continue to be followed up as part of the study.

We recommend avoiding strenuous exercises and activities for two weeks after vaccination.


What is your advice for parents who are still undecided?

Assoc Prof Thoon: Having seen what children with severe infection or severe MIS-C go through during their stay in the hospital, we, as well as parents, ask ourselves whether there could have been anything done to try and prevent the child from experiencing this.

We have also witnessed young babies and neonates who were just a few days old being admitted into the intensive care and placed on ventilator support due to COVID-19 infections and complications.

We acknowledge that the disease has been mild in the vast majority of children. However, we should be mindful that the virus is continuing to mutate and evolve. With each successive mutation and an increasing number of variants emerging, more children are becoming more susceptible to infection and complications.

As we progressively open up and people interact with one another, it is a question of time before we will meet the virus. We believe it is not a choice between vaccinating or not vaccinating – it is the question of whether we are going to try to offer our children an opportunity to be protected against an infection and the disease or face the risk of an infection. We should desire to protect and prevent children from an infection as far as we can.


Information and statistics accurate as at 3 February 2022.



  1. Child vaccination. Ministry of Health. (2021). Retrieved January 12, 2022, from https://www.moh.gov.sg/covid-19/vaccination/faqs---children-related-vaccination-matters
  2. Ministry of Health. (2022). Brochure: COVID-19 Vaccination for Children 5-11. Singapore, Singapore. Retrieved January 12, 2022, from https://www.moh.gov.sg/docs/librariesprovider5/vaccination-matter/child-vax_brochure_v2_2jan-(2-edits).pdf
  3. COVID-19 Vaccination for Children. Ministry of Health. (2022, January 10). Retrieved January 12, 2022, from https://www.moh.gov.sg/news-highlights/details/covid-19-vaccination-for-children
  4. Media Statement on Paediatric MIS-C Cases in Singapore. Ministry of Health. (2021, November 6). Retrieved January 12, 2022, from https://www.moh.gov.sg/news-highlights/details/media-statement-on-paediatric-mis-c-cases-in-singapore
  5. Opening Remarks by Minister for Health Mr Ong Ye Kung at COVID-19 Multi-Ministry Taskforce Press Conference on 8 November 2021. Ministry of Health. (2021, November 8). Retrieved January 12, 2022, from https://www.moh.gov.sg/news-highlights/details/opening-remarks-by-minister-for-health-mr-ong-ye-kung-at-covid-19-multi-ministry-taskforce-press-conference-on-8-november-2021
  6. Children aged below 12 starting to make up the majority of Covid-19 cases admitted into hospitals. The Straits Times. (2022, January 21). Retrieved February 3, 2022, from https://www.straitstimes.com/singapore/children-aged-below-12-starting-to-make-up-the-majority-of-covid-19-cases-admitted-into-hospitals


Associate Professor Thoon Koh Cheng, Head and Senior Consultant, Infectious Disease Service, KKH

Head of the Infectious Disease Service, and Chairperson of the Hospital Infection Control Committee at KKH, Assoc Prof Thoon is also Chairman of the Ministry of Health’s National Verification Committee for Measles Elimination.

Assoc Prof Thoon’s research interests include epidemiology of vaccine-preventable diseases, respiratory viral diseases, antimicrobial stewardship, infection control and adverse events following immunisation.

Dr Sylvia Choo, Senior Consultant, Department of Child Development, KKH

Senior Consultant with the Department of Child Development at KKH, Dr Choo’s areas of focus include family-centred care, parent-mediated intervention, and the integration and right-siting of care and early intervention for children with developmental needs.

Dr Choo and team undertook a Ministry of Health Team Fellowship in 2016 at the Frank Porter Graham Child Development Institute, University of North Carolina, United States to examine the integration and continuity of care for children presenting with developmental and behavioural issues.