HSA approves Pfizer’s Comirnaty Covid-19 vaccine for use in children aged under 5

SINGAPORE — The Health Sciences Authority (HSA) on Wednesday (Sept 28) authorised the use of Pfizer’s Comirnaty Covid-19 vaccine in children aged six months through four years, making it the second vaccine approved for young children in Singapore.

The HSA said in a press release on Thursday that the vaccination regimen for the primary series in this age group consists of three 3-microgram doses.

This means that the first two doses will be administered three weeks apart, followed by a third dose to be administered at least eight weeks after the second dose.

The authority added that official vaccination recommendations on the use of this vaccine will be issued by the expert committee on Covid-19 vaccination and the Ministry of Health (MOH) when ready.

Last month, HSA extended the authorisation of Moderna's two-dose Spikevax Covid-19 vaccine for children aged six months to five years.

In response to media queries, MOH said on Thursday that Moderna's Spikevax vaccine will be available next month, while Pfizer's Comirnaty vaccine is expected to be available by the end of the year.

"Vaccinations and boosters remain a critical part of our strategy in ensuring our children are well-protected against severe illness, should they be infected with Covid-19. We encourage everyone who is eligible to be vaccinated when it is offered to them," it added.

In authorising the use of Pfizer's Comirnaty Covid-19 vaccine for children aged six months through four years, HSA said that it carefully considered the clinical data and “assessed that the benefits outweighed the risks”.

The clinical data was based on an ongoing Phase 2/3 study conducted by Pfizer, involving about 1,800 participants in this age group.

The results, HSA said, showed that the immune response in young children with a three-dose primary series was comparable to that in individuals aged 16 to 25 years who received two higher doses of 30 micrograms as the primary series vaccine.

“Hence, it can be inferred that three doses of the vaccine may provide a similar level of protection in young children as that of two doses in adults,” it added.

HSA also said that real-world data here of children aged five to 11 years who received two doses of the Pfizer vaccines showed that vaccine effectiveness against the Omicron coronavirus strains was estimated to be around 40 per cent for symptomatic disease and remained high at more than 80 per cent for protection against Covid-related hospitalisations.

“Hence, it could reasonably be expected that the vaccine would similarly protect younger children aged six months through four years from severe outcomes of Covid-19 such as multi-system inflammatory syndrome (MIS-C), and other potential complications.”

MIS-C is a rare syndrome linked to a previous infection of the coronavirus.

The authority added that there was preliminary data from a secondary analysis of Covid-19 cases in the clinical study as well, which suggested that the vaccine efficacy was estimated to be around 73 per cent.

“However, the evidence was limited and should be interpreted with caution.” 

As for side effects in young children, HSA said that safety data from the clinical studies showed that they were similar to those reported in adults.

“The adverse events were mild to moderate and commonly reported with childhood vaccination, such as injection site pain, fever, fatigue and headache.

“These reactions are generally associated with vaccinations and expected as part of the body’s natural response to build immunity against Covid-19. They usually resolve on their own within a few days.”

There were no cases of serious adverse events such as myocarditis or pericarditis — both are forms of heart inflammation — reported in the clinical study with Comirnaty.

However, HSA recommends that caregivers of young children should monitor for signs and symptoms of myocarditis such as chest pain, breathing difficulty and so on, as well as take precautions to minimise rigorous physical activity following vaccination.

On its end, HSA said that it will continue to actively monitor the safety of the vaccine and require Pfizer to submit data from the ongoing clinical study to ensure that the benefits of the vaccine continue to outweigh the risks.

“HSA will take the necessary actions and provide updates to the public if any significant safety concerns are identified.”

Health Minister Ong Ye Kung said earlier this month that the vaccine roll-out for children under five years old, as well as booster shots for those from six years to 11 years old, will begin late October or early November.