Since the booster programme was rolled out on Sep 15, a total of 3,194,494 have received these jabs as of Jan 31, said HSA.
In this category, there were 553 adverse events reports (0.03 per cent of doses administered) associated with the use of the PfizerBioNTech/Comirnaty vaccine and 289 such reports (0.03 per cent of doses administered) with the Moderna/Spikevax vaccine.
There were also 73 serious adverse event reports (0.002 per cent of administered doses), of which 15 cases were myocarditis and pericarditis – inflammation of the heart muscles and outer lining of the heart respectively.
ADVERSE EVENTS OF SPECIAL INTEREST
HSA said that it is closely monitoring several adverse events of special interest, including anaphylaxis, myocarditis, pericarditis and cerebral venous thrombosis.
So far, the incidence rate of anaphylaxis reported locally with the vaccines has remained “low and stable” at about 0.89 per 100,000 doses administered, said HSA.
Of the 88 cases of anaphylaxis reported with the mRNA vaccines, all the patients recovered after medical treatment, said the authority.
It added that the number of cases of anaphylaxis associated with the second dose was lower than with the first dose of mRNA vaccines. To date, HSA has not received any cases of anaphylaxis associated with the booster dose.
For myocarditis and pericarditis, HSA said that it has as of end-January received 115 reports following the administration of mRNA vaccines. These cases happen more frequently in younger males below 30 years old, and more often with the second dose, said HSA.
One case of myocarditis with Sinovac-Coronavac vaccine has also been reported.
“Most cases are mild, with individuals reported to have recovered or are recovering,” said the authority.
“It should be noted that COVID-19 infection is also known to be associated with myocarditis,” HSA added.
There have been rare cases of cerebral venous thrombosis (CVT), or blood clots occurring in the veins of the brain, reported with the mRNA vaccines.
As of end-January, HSA has received 13 suspected reports of cerebral venous thrombosis with such vaccines.
“Vaccines are the best way to protect people from COVID-19 and have already saved many lives,” said HSA.
“HSA’s current assessment is that the overall benefits of the Pfizer-BioNTech/Comirnaty, Moderna/Spikevax and Sinovac-CoronaVac COVID-19 vaccines in preventing COVID-19 and serious complications associated with COVID-19 far outweigh any currently known adverse events,” it added.