0.13% of Covid-19 mRNA vaccine doses administered in S'pore linked to suspected adverse events

As at Aug 31, more than 8.7 million doses of the Pfizer-BioNTech and Moderna mRNA vaccines have been administered.
As at Aug 31, more than 8.7 million doses of the Pfizer-BioNTech and Moderna mRNA vaccines have been administered.PHOTO: ST FILE

SINGAPORE - The rate of suspected adverse events linked to the Covid-19 vaccines under the national vaccination programme is 0.13 per cent, said the Health Sciences Authority (HSA) on Thursday (Sept 16).

The rate of serious adverse events, such as anaphylaxis, is much lower, at 0.006 per cent.

For the national programme, 8,716,085 doses of the Pfizer-BioNTech and Moderna mRNA vaccines have been administered as at Aug 31, and 11,737 suspected adverse reactions were reported in the same period.

Of these, 498 reports were classified as serious adverse events.

The report - the fifth safety update for the Pfizer and Moderna vaccines under the national vaccination programme - also included an update on the Sinovac-CoronaVac shot under the special access route, for the second time.

There have been 90 reports of suspected adverse reactions to the Sinovac-CoronaVac vaccine, including five serious ones, as at Aug 31.

With 168,439 doses of the vaccine administered in the same period, this amounts to a rate of 0.053 per cent for suspected cases, and about 0.003 per cent for serious ones. These serious events were: one report each of Bell's Palsy, serious allergic reaction and vertigo with ringing of the ears, and two reports of anaphylaxis.

The HSA said: "The type and number of reports received for the different Covid-19 vaccines are not directly comparable as the vaccines may have been used in the vaccination programme for different lengths of time, and may have been administered to different numbers of people, with different underlying medical conditions and across different settings."

For the Pfizer and Moderna vaccines, the most commonly reported symptoms were consistent with those typically observed following vaccination.

They include dizziness, shortness of breath, chest tightness or discomfort, palpitations, injection site reactions such as pain and swelling, fever and allergic reactions - such as rashes, itching, hives and swelling of eyelids, face and lips.

These typically resolve within a few days, said HSA.

Among the serious cases, the most frequently reported were anaphylaxis and other severe allergic reactions.

The most commonly reported symptoms among those aged 12 to 18 include rash, hives, swelling of the eyelids, face and lips, chest tightness or discomfort, shortness of breath, fever, dizziness and light-headedness, HSA said.

Fainting or temporary loss of consciousness has also been reported, particularly in this age group.

However, it is generally triggered by anxiety and fear of pain during the vaccination process rather than by the vaccines, the agency pointed out, and the local incidence rate for fainting in those aged 12 to 18 is similar to overseas reports.

Rare instances of anaphylaxis, a severe life-threatening allergic reaction, have also been linked to the Covid-19 vaccines.

"It is a known adverse reaction associated with vaccines in general," said HSA, adding that the incidence rate of anaphylaxis locally is similar to those reported overseas.

HSA also said rare cases of myocarditis and pericarditis have been reported with mRNA Covid-19 vaccines both overseas and locally.

"They are caused by inflammation of the heart muscles and outer lining of the heart, respectively.

"Myocarditis and pericarditis are not heart attacks, which are usually caused by blockage of the blood vessels that supply the heart," said HSA.

"It is important to note that heart attacks and strokes occur naturally within our population, regardless of whether people are vaccinated.

"The frequency of heart attacks and strokes in vaccinated persons locally is within the background incidence rates and, to date, there is no evidence that the vaccines can directly cause these events."

Cases of Bell's Palsy, which refers to facial muscle weakness caused by inflammation of the facial nerve, have also been observed in some vaccine recipients.

Generally, patients will recover completely from it even without treatment, and the incidence rate for Bell's Palsy is within the background incidence.

Based on the data to date, the benefits of the Pfizer-BioNTech and Moderna Covid-19 vaccines continue to outweigh the known risks in a pandemic, said HSA.

It added that it will continue to actively monitor the safety profile of the Covid-19 vaccines and relevant regulatory actions will be taken to safeguard public health.