SINGAPORE - There were four cases of adverse reactions out of the 2,792 Novavax Covid-19 vaccine doses administered in Singapore as at May 31 - but they were non-serious, said the Health Sciences Authority (HSA).
They experienced rash, chest pain, dizziness and blood vessel inflammation (vasculitis), it said on Monday (June 27).
"These are largely consistent with what was reported in the clinical studies and are known adverse effects associated with vaccines," it added.
The authority said none of the four cases required hospitalisation.
HSA said it is monitoring closely the incidence rate of myocarditis (inflammation of heart muscles) and pericarditis (inflammation of the outer lining of the heart), given that a small number of such reports has been observed from ongoing clinical trials so far.
No reports of myocarditis have been reported to date with the Novavax vaccine, it noted.
HSA added that published literature has shown that Covid-19 infection is also known to be associated with myocarditis, and that 40 extra myocarditis events per million people were observed among those infected with the virus.
Therefore, the possibility of myocarditis risk following inoculation with the Novavax vaccine cannot be excluded, though the benefits of being vaccinated still outweigh the risk of doing so.
As a precautionary measure, those who have been vaccinated with Nuvaxovid should avoid strenuous physical activity or exercise for two weeks after getting the shot to mitigate the risk of myocarditis.
These include running, weightlifting, competitive sports and ball games.
The Expert Committee on Covid-19 Vaccination has recommended that individuals aged 18 and above receive the Nuvaxovid vaccine for their primary series or booster vaccination, although the mRNA vaccines remain the preferred vaccines due to their higher efficacy and stronger immune response generated.
Those who are medically ineligible to receive the mRNA vaccines should consider Nuvaxovid.
HSA added in its update that the incidence rates of adverse events such as anaphylaxis, myocarditis, pericarditis and cerebral venous thrombosis (blood clotting in the brain) with the mRNA vaccines have stabilised.
However, 21 cases of appendicitis (inflammation of the appendix) have been reported in people who received the Pfizer vaccine, among more than 11 million doses administered.
HSA found a small increased incidence rate of appendicitis occurring within 21 days of the primary vaccination series, mainly in those aged 12 to 17.
No increased cases have been observed in those who received Pfizer as their booster dose.
It added that the background incidence rate of appendicitis in Singapore is about 100 cases per 100,000 people a year, and that rare cases of appendicitis have been reported following Covid-19 vaccination globally.