SINGAPORE —  Eight suspected "adverse events" had been found as at Dec 31 last year among children aged six months to four years who had received 16,448 doses of the Covid-19 Moderna-Spikevax vaccine, the Health Sciences Authority (HSA) said on Thursday (Feb 2).

That is an adverse event reporting rate of 0.05 per cent for this young age bracket, to whom the vaccination was rolled out on Oct 25 last year.

On that same date, the Pfizer-BioNTech (Comirnaty) vaccine was made available as booster doses for children aged five years to 11 years. Among the 81,477 doses administered as at Dec 31 last year, there had been 26 suspected adverse events reported.

For that age bracket, the adverse event reporting rate was 0.03 per cent, HSA added.

An adverse event is any undesirable medical condition that occurs after taking the vaccine, and it has to be reported by healthcare providers to the authority.

HSA noted that so far, the number of doses of the two vaccines to this younger age bracket is relatively small.

However, it said that "based on our assessment of current local and overseas data, no new safety signals have been identified with the use of the vaccines in this age group".

Of the eight suspected adverse events among the group aged six months to four years, five were serious cases where the children experienced fits, Kawasaki disease (swelling of blood vessels), fever and vomiting, HSA said. 

An adverse event is classified as serious when the patient has to be hospitalised, has experienced a significant reduction in functioning level, develops a life-threatening illness or results in birth defects due to the vaccination. 

All the children have recovered or were recovering at the time of report, HSA added. 

The adverse events reported among those aged five to 11 were mostly non-serious cases such as fever, headache, palpitations, joint pain and vomiting.

However, there were two serious cases, one involving myocarditis, which refers to the inflammation of the heart muscles, and another involving a drop in platelet count. 

Both children were recovering at the time of report, HSA said. 

It added that it is also closely monitoring overseas cases within the same age group, which resulted in myocarditis associated with booster doses of the Covid-19 vaccines that use messenger ribonucleic acid (mRNA) technology, namely the Pfizer-BioNTech and Moderna ones.

However, HSA said that the incidence remains rare and is generally lower compared to adolescents and adults. 

BIVALENT VACCINES

Since the rollout of the bivalent vaccines around the end of last year, 482,666 doses of the Moderna-Spikevax bivalent vaccine and 202,382 doses of the PfizerBioNTech (Comirnaty) bivalent have been administered. 

Out of the 59 adverse events reported for the Moderna-Spikevax bivalent vaccine, six were classified as serious cases.

There were two serious cases out of the 11 adverse events reported for the Pfizer-BioNTech (Comirnaty) bivalent jab. 

The serious cases involved symptoms such as serious allergic reactions, hypotension with tachycardia (fast heartbeat) and hearing loss. 

For the rest of the cases, the symptoms reported were similar to those following the monovalent vaccines, which were mostly "non-serious" adverse events such as allergic reactions, fever, giddiness and chest discomfort, HSA said. 

"The serious adverse events reporting rates for the two vaccines are similar, at 0.001 per cent, which is lower compared to the monovalent vaccines at 0.007 per cent," it added. 

UPDATE ON VACCINE DOSES 

Providing updates on the number of Covid-19 vaccination doses administered, HSA said that a total of 17,191,955 doses of Covid-19 vaccines had been administered as of Dec 31 last year.

The majority (88.1 per cent) of the doses administered were the monovalent mRNA vaccines since these were the first vaccines that were made available and recommended for use in Singapore, it said. 

A total of 10,506,824 primary doses, 4,682,058 first booster doses and 1,239,781 second booster doses of the mRNA vaccines have been administered.

The reporting rates of adverse event and serious adverse event for the mRNA vaccines, which included both the monovalent and bivalent versions, remained rare at 0.11 per cent and 0.007 per cent respectively.

The serious adverse event reporting rates for the first booster doses was at 0.004 per cent and for the second dose, 0.001 per cent.

These were lower compared to the reporting rate for the primary doses, which was at 0.009 per cent. 

For the Sinovac-CoronaVac and Sinopharm Covid-19 vaccines, 722,419 doses of the inactivated vaccines have been administered and the serious adverse event reporting rate remained rare at 0.006 per cent. 

For the Nuvaxovid Covid-19 vaccine, 40,873 doses have been administered and the serious adverse event reporting rate remained rare at 0.02 per cent.

HSA said that the benefits of the Pfizer-BioNTech (Comirnaty), Moderna-Spikevax, Nuvaxovid and Sinovac-CoronaVac Covid-19 vaccines continue to outweigh the known risks. 

"Vaccination has been demonstrated to be the most effective way to reduce deaths and severe illness from Covid-19 infection and has enabled Singapore to ease most of the safe management measures," it added.