Adverse effects after receiving bivalent COVID-19 vaccines rare, says HSA

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Adverse effects after receiving bivalent COVID-19 vaccines rare, says HSA

SINGAPORE: Adverse effects after receiving the bivalent COVID 19 vaccine shots are rare, according to a Health Sciences Authority safety update released on Thursday. The authority received 59 and 11 adverse event reports for the Moderna Spikevax COVID 19 bivalent vaccine and Pfizer-BioNTech Comirnaty COVID 19 bivalent vaccine.

Since it was rolled out in Singapore on October 14 last year, more than 482,600 doses of Moderna have been administered, while more than 202,300 Pfizer-BioNTech bivalent jabs have been given since December 12, 2022.

The HSA saw an adverse event reporting rate of 0.012 per cent for the Moderna bivalent vaccine and a smaller 0.005 per cent for the Pfizer-BioNTech bivalent vaccine.

The adverse events reported for the bivalent mRNA vaccines were similar to those reported by those who took the monovalent vaccine. Other non-serious adverse events include a rash, eyelid swelling, fever, giddiness, chest discomfort, or an increase in blood pressure.

There were six serious adverse events reported for the Moderna bivalent vaccine and two such events for the Pfizer-BioNTech bivalent vaccine.

HSA said that these include serious allergic reactions, anaphylaxis, myocarditis, hypotension with tachycardia fast heartbeat and hearing loss.

A serious adverse event is classified as serious when it results in hospitalization, a significant reduction in functioning level, a life-threatening illness or death.

The serious adverse events reporting rates for the two bivalent vaccines are similar, at 0.001 per cent.

The vaccines were rolled out on December 30, 2020, and until December 31, 2022, according to HSA's latest update. This is the first HSA safety update to include data on the bivalent shots.

More than 10.5 million primary doses, 4.6 million first booster doses and 1.2 million second booster shots have been administered in Singapore as of December 31, 2022, according to the monovalent mRNA vaccines.

The reporting rates of adverse and serious adverse events for the mRNA vaccines were very rare, at 0.11 per cent 17,741 reports and 0.007 per cent 1,119 reports respectively.

There were 173 serious adverse event reports 0.004 per cent for the first booster jab and 17 such reports 0.001 per cent for the second booster shot.

The Moderna vaccine was rolled out on October 25 last year as a primary vaccine for children aged six months to four years, while the Pfizer-BioNTech jab was made available as a booster for children aged five years to 11 years.

More than 16,000 doses of Moderna vaccine have been given to children aged six months to four years, and more than 81,000 Pfizer-BioNTech boosters have been given to children aged five years to 11 years.

HSA said that serious adverse events after COVID 19 vaccination in children aged six months to 11 years are rare.

There were eight adverse event reports after children aged six months to four years took the Moderna jab, including five serious events that included fever, vomiting, fits, and Kawasaki disease the swelling of blood vessels.

Rare events that have been reported following childhood vaccination can be associated with childhood illnesses, such as febrile seizures and Kawasaki disease. HSA said all the children had recovered or were recovering at the time of the report.

There were 26 adverse event reports from the Pfizer-BioNTech booster for children aged five years to 11 years with a reporting rate of 0.03 per cent. This was lower than the adverse event reporting rate for the primary vaccine series in this age group, which stood at 0.15 per cent.

There were two serious adverse events, with one describing myocarditis the inflammation of heart muscles and the other a drop in platelet count.

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