• As of Oct 31, 854,268 Covid-19 booster shots had been administered, HSA said
• Of those, a total of 200 reports of suspected adverse events were received
• That represented just 0.02 per cent of the booster shots administered, the agency added
• A total of just over 9.95 million mRNA Covid-19 vaccine doses had been administered as of Oct 31
• Of those, 13,334 reports of adverse events were received

SINGAPORE — As of Oct 31, there were a total of 200 reports of suspected “adverse events” experienced by people who received Covid-19 vaccine boosters, up from 14 in the  last report by the Health Sciences Authority (HSA), which covered only the first two weeks of the booster programme up until Sept 30.

In its seventh safety report, HSA said on Tuesday (Nov 16) that the 200 reports were out of a total of 854,268 booster shots administered since the national Covid-19 booster vaccination programme was rolled out on Sept 15. These were boosters from messenger ribonucleic acid (mRNA) vaccines of Pfizer-BioNTech or Moderna.

The latest number represents just 0.02 per cent of Covid-19 booster shots administered. 

The adverse events reported for the booster shots were largely similar to those reported for the first two doses of the two mRNA vaccines and there was no observed increase in frequency of events, HSA said.

An adverse event for vaccination is any undesirable medical condition that occurs after taking the vaccine, which does not necessarily have a direct link to it. It may be coincidental or related to an underlying or undiagnosed disease.

Adverse events are reported by healthcare professionals to HSA when they suspect that the adverse events may be associated with the vaccine.

Commonly reported adverse events included rash, angioedema (swelling of the eyelids, face and lips), chest discomfort, palpitation, shortness of breath, fever, generalised weakness and dizziness.

Of the 200 suspected adverse events as at Oct 31, there were 10 suspected serious cases, or 0.001 per cent of doses administered — up from two or 0.0008 per cent as at Sept 30.

SAFETY UPDATE FOR MRNA VACCINES

A total of 9,953,673 doses of the Pfizer-BioNTech and Moderna vaccines had been administered as of Oct 31. Of these, HSA has received 13,334 reports of suspected adverse events.

This represents 0.13 per cent of the total doses administered and is just a tad lower than the 0.14 per cent proportion reported in the update last month.

About 78 per cent of the suspected adverse events reported were among people younger than 60. Of the total suspected adverse events, 66 per cent were experienced by women.

Generally, younger people have more active immune responses and may experience more adverse events to the vaccines, HSA said.

Suspected serious adverse events made up 634 or 0.006 per cent of administered doses, the same percentage as stated in the last update.

The most frequently reported serious adverse events were anaphylaxis, a type of life-threatening allergic reaction, with 86 reports. For other severe allergic reactions, there were 52 reports.

Other serious suspected adverse events included breathing difficulty, fast heart rate, nerve inflammation, limb numbness, blood clots, chest discomfort and menstrual disorder.

REACTIONS IN CHILDREN AGED 12 AND OLDER

Among children between 12 and 18 years old who took mRNA vaccines, HSA received 798 reports of suspected adverse events, which make up 0.13 per cent of the doses administered to them since the rollout of the programme to students on June 3.

This represents a similar level to the 0.1 per cent reported in the last update.

ADVERSE EVENTS OF SPECIAL INTEREST

Anaphylaxis, Bell’s palsy, myocarditis and pericarditis are examples of what HSA terms “adverse events of special interest”, which is a “medically significant event that has been observed historically with other vaccines”.

Anaphylaxis

There were 86 cases of anaphylaxis reported with the Pfizer-BioNTech and Moderna vaccines, and all the patients were reported to have recovered after medical treatment.

The incidence rate of anaphylaxis reported here with the vaccines is about 0.94 for every 100,000 doses administered and this is similar to the incidence rates reported overseas.

Myocarditis and pericarditis

There were 86 cases of myocarditis and pericarditis, which refer to an inflammation of the heart muscle and outer lining of the heart respectively, following more than 9.95 million doses of vaccines administered.

The risk is observed to be highest in younger males aged 30 years and below, with an incidence rate of 3.69 for every 100,000 doses administered. For females from the same age group, it was an incidence rate of 0.47 for every 100,000 doses administered.

Of the 49 cases that occurred in people aged 30 years and below, 44 or 90 per cent were males. All the patients were reported to have recovered or are recovering.

HSA added that the risk of myocarditis and pericarditis is also observed to be higher with the second dose of an mRNA vaccine, comprising 64 per cent of the reported cases.

The incidence rate was:

• 5.8 for every 100,000 doses administered in those aged 12 to 19 
• 2.0 for every 100,000 doses administered in those aged 20 to 29
• 0.61 for every 100,000 doses administered in those aged 30 years and above

Cerebral venous thrombosis

Cerebral venous thrombosis is a rare type of blood clot that occurs in the veins of the brain.

There were 13 suspected cases of cerebral venous thrombosis reported with the Pfizer-BioNTech and Moderna vaccines.

None of the cases had a fatal outcome, HSA said.

The adverse events reported to be associated with Covid-19 showed an incidence rate of 8.4 for every 100,000 in a study here.

Bell’s palsy

There were 109 cases of Bell’s palsy, an inflammation of the facial nerve, reported with the Pfizer-BioNTech and Moderna vaccines, with most cases not being serious.

The incidence rate here is within the background incidence. Data to date does not suggest an increased risk following vaccination.

SAFETY UPDATE FOR OTHER VACCINES

For the Sinovac-CoronaVac vaccine, HSA said that it has received 171 reports of suspected adverse events, including 14 serious ones, out of a total of 206,722 doses of the vaccine being administered here as of Oct 31.

This represents a 0.08 per cent of administered doses out of the total doses administered.

As for the Sinopharm vaccine, HSA has received 17 reports of suspected adverse events, including one serious case, out of 48,697 doses administered as of Oct 31.

This represents a 0.03 per cent of administered doses out of the total.

“Most of the adverse events are largely expected with vaccination and reflect what has been reported in the clinical trials,” HSA said.

It maintains its current assessment that the benefits of the Pfizer-BioNTech, Moderna and Sinovac-CoronaVac vaccines against Covid-19 continue to outweigh the known risks in this pandemic.