More than 18,000 Novavax Covid-19 shots given, with rare serious reactions: HSA

HSA said those who receive the Novavax vaccine should avoid strenuous physical activity or exercise for two weeks after vaccination PHOTO: REUTERS

SINGAPORE - Out of the 18,073 doses of the Nuvaxovid Covid-19 vaccine  administered as part of Singapore's vaccination programme as at Aug 31, 28 reports of adverse effects were received.

Of these reports, just five were serious, with four cases of anaphylaxis and one of serious allergic reaction, the Health Sciences Authority (HSA) said on Monday.

Anaphylaxis is a rare and potentially life-threatening allergic reaction that can occur following vaccination in certain susceptible individuals.

According to HSA, these reactions occurred in susceptible individuals who had previous allergic reactions or adverse effects to the Pfizer/Comirnaty and Sinovac-CoronaVac Covid-19 vaccines, as well as a history of drug or food allergies.

It added that all the patients have recovered from the serious adverse reactions.

Nuvaxovid, better known as Novavax, contains a version of the spike protein of the original Sars-CoV-2 virus strain and works by building up a recipient’s immune system. 

The total doses of Novavax constitute just 0.1 per cent of the nearly 16 million doses of Covid-19 vaccines that have been administered to the population.

There were no local reports of myocarditis or pericarditis observed with individuals who received a dose of Novavax, said HSA, noting that a small number of reports overseas were due to higher exposure of the population to the vaccine.

HSA said those who receive the Novavax vaccine should avoid strenuous physical activity or exercise for two weeks after vaccination, to mitigate the potential risk of myocarditis.

It added: "Safeguards such as pre-vaccination screening, post-vaccination observation period and ensuring that all vaccination centres are medically equipped and staffed by qualified medical professionals are in place to mitigate this risk."

These are similar to the measures taken for mRNA vaccines, which include the Pfizer/Comirnaty and Moderna vaccines, HSA said.

The incidence of adverse reactions to Covid-19 vaccines remains low, with 17,499 reports of adverse effects made by those who were given mRNA vaccines.

This makes up 0.12 per cent of the 15,149,498 doses of mRNA vaccines that have been administered.

Only 1,075 individuals, or 0.007 per cent, reported serious reactions to a dose of mRNA vaccines.

According to HSA, mRNA vaccines make up the vast majority of the vaccine doses administered, at 95.9 per cent. Inactivated Covid-19 vaccines like the Sinovac-CoronaVac and Sinopharm vaccines make up 4 per cent of the doses.

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