Rare to experience serious adverse effects to vaccines: HSA

95 serious cases so far suspected to be reactions to Covid-19 vaccination

There were 95 serious cases suspected to be reactions to Covid-19 vaccination here over a period of less than four months, and 20 of these involved a potentially life-threatening allergic reaction known as anaphylaxis, the Health Sciences Authority (HSA) said yesterday.

But the 95 cases represent just 0.004 per cent of the more than 2.2 million doses administered from Dec 30 to April 18, the HSA said in its first update on the safety of the mRNA Covid-19 vaccines used here.

About 0.13 per cent of the doses administered resulted in suspected adverse reactions. About 70 per cent of these cases involved people who were younger than 60 years old, although they made up about half of the people who have taken the vaccines.

There were no deaths associated with taking the vaccine.

There were also no reports of unusual blood clots associated with low platelets that have been reported with other types of Covid-19 vaccines overseas, said the HSA.

It defines an adverse effect as serious when it results in hospitalisation, a significant reduction in functional capacity, a life-threatening event like anaphylaxis, or death.

Most of the adverse events were associated with the Pfizer-BioNTech vaccine because this was available since Dec 30. The Moderna vaccine was rolled out only on March 12.

Anaphylaxis, which typically happens very quickly, remained the greatest concern because it is life-threatening, said the HSA.

Within minutes of getting the vaccine, a person who has it may experience swelling of the face, eyes and lips. Their airway can be constricted, and there may be nausea, vomiting and diarrhoea.

The 20 cases were in people aged 23 to 68, mostly women. About 55 per cent of them had a history of allergies, to food or drugs. And 60 per cent of them had an onset of symptoms within 30 minutes. All have recovered after medical treatment, said the HSA.


The incidence rate of this reaction here is about 1.4 per 100,000 doses administered, which is similar to the incidence rates reported overseas, of around 0.5 to two per 100,000 doses administered.

Anaphylaxis is a reaction that has been reported with the use of other vaccines too, as is Bell's Palsy, which is a temporary paralysis of a part of the facial muscles. HSA is monitoring this closely.

There have been 25 cases of Bell's Palsy and most are not serious, it said.

Most patients recover completely, even without treatment.

Among the 95 with serious adverse events, another 20 had severe allergic reactions, including severe rashes, possible shortness of breath and rapid heartbeat.

The rest experienced breathing difficulty, fast heart rate, an increase or decrease in blood pressure, chest discomfort, fainting, limb numbness or pain for a few days, changes in vision and increase in liver enzymes, said the HSA update.

Most of the 95 people have recovered or are recovering.

They are among a bigger group of 2,796 people who experienced adverse effects associated with the vaccine, according to HSA data.

This article first appeared in The Straits Times.

No spike in heart attacks or strokes in vaccinated people: HSA

There has been no uptick in heart attacks or strokes in vaccinated people and no evidence that the Covid-19 vaccines used here can directly cause them, the Health Sciences Authority (HSA) said yesterday.

"A greater frequency of heart attacks and strokes has not been observed in vaccinated persons locally, and to date, there is also no evidence the vaccines can directly cause these events," HSA said in its first update on the safety of the mRNA vaccines used here.

Only the Pfizer-BioNTech and Moderna vaccines are used here.


Because of the large number of people being vaccinated, some may, by chance, experience medical events such as heart attacks and strokes in the following days or weeks. And this may not be related to the vaccination, said HSA.

At a Health Ministry briefing yesterday, an HSA spokesman said it is hard to ascribe causality to heart attacks or strokes as they can happen spontaneously, and generally, such patients do have underlying medical conditions.

Prof Teo Yik Ying, dean of the National University of Singapore's Saw Swee Hock School of Public Health, said at the briefing that typically, in a three-month period, there would be some 2,000 stroke cases and slightly fewer than 3,000 heart attack cases.

People can experience these, whether they are vaccinated or not.

"There have not been any established links between cases of stroke or heart attack with either the Pfizer or Moderna vaccines in the United States, which has seen at least 240 million doses delivered as of May 5," he said.

"The signal from the Tan Tock Seng Hospital cluster is that vaccination helps because it provides much better protection against serious outcomes of infection."

Yesterday, MOH said it had received and was processing applications for the Vaccine Injury Financial Assistance Programme for Covid-19 Vaccination (Vifap).

Under Vifap, which was launched on March 17, those who need inpatient treatment and medical intervention, and who subsequently recover, will get $2,000.

Those who require admission to high dependency or intensive care wards, and subsequently recover, will get $10,000.

Those who die or suffer permanent severe disability as a result of the vaccination will get $225,000. - THE STRAITS TIMES