47 ‘adverse events’ reported out of more than 104,000 doses of Sinovac vaccine: HSA
By ASYRAF KAMIL
Published AUGUST 16, 2021
Updated AUGUST 17, 2021
- HSA received reports of 47 adverse events from more than 104,000 doses of the Sinovac vaccine given
- There were some 9,400 suspected adverse events reports linked to the Pfizer-BioNTech and Moderna vaccines as of July 31
- Of these, 389 — or 0.005 per cent of doses administered — were classified as “serious” adverse events
- About 78 per cent of the adverse events were reported in people who were younger than 60 years old
SINGAPORE — A total of 47 “adverse events” have been reported from more than 104,000 doses of the Sinovac-CoronaVac vaccine that have been administered in Singapore as of July 31.
In a news release on Monday (Aug 16), the Health Sciences Authority (HSA) said that four out of the 47 adverse events were “serious reports”.
They included one report each of Bell’s palsy, a condition that causes temporary weakness or paralysis of the facial muscles, anaphylaxis or the rapid onset of severe allergic reactions, vertigo with ringing of the ears, and serious allergic reactions, the authority 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 the treatment. They may be coincidental or related to an underlying or undiagnosed disease. These have to be reported by healthcare providers to HSA.
It stressed that the adverse events were consistent with those typically observed following vaccination.
“HSA will continue to monitor the adverse events with Sinovac-CoronaVac vaccine.”
The China-made Sinovac-Coronavac vaccine was earlier placed on HSA’s special access route on June 2 for people with specific medical needs. People began getting themselves immunised with the vaccine from June 18.
SAFETY UPDATE FOR MRNA VACCINES
HSA said on Monday that it has received 9,403 suspected adverse events reports associated with the usage of the Pfizer-BioNTech and Moderna vaccines as of July 31.
A total of 7,567,466 vaccine doses had been given, and the suspected adverse events comprise 0.12 per cent of administered doses.
This was its fourth safety update on the messenger ribonucleic acid (mRNA) vaccines since the voluntary national vaccination exercise began last December.
The percentage of suspected adverse events is on par with HSA’s last safety update in July, when there were 6,606 suspected adverse events that made up 0.12 per cent of administered doses as well.
The authority noted that about 78 per cent of the adverse events were reported in people who were younger than 60 years old.
“Generally, younger individuals have more active immune responses and may experience more adverse events to the vaccines.
“This is part of the body’s natural response to build immunity against Covid-19. About 66 per cent of the adverse events were reported in females,” it said.
It added that the most commonly reported adverse events were consistent with those typically observed following vaccination.
These include injection site reactions such as pain and swelling, fever, dizziness, shortness of breath, chest tightness or discomfort and allergic reactions such as rash, itch, hives and swelling of eyelids, face and lips.
REACTIONS IN STUDENTS AGED 12 AND OLDER
As of July 31, HSA said that it has received reports of 383 adverse events associated with the use of the Pfizer-BioNTech vaccine among adolescents aged 12 to 18, which is 0.08 per cent of doses administered.
The 0.08 per cent is slightly higher than the 0.06 per cent reported in the previous safety update last month.
The commonly reported adverse events within this age group include rash, hives, shortness of breath, fever, dizziness, lightheadedness and syncope, the medical term for fainting and temporary loss of consciousness.
“(These) generally resolved within a few days and they are also in line with the events reported overseas,” HSA said.
Syncope occurring after vaccination is “not uncommon in adolescents”, it added.
There were 25 reports of syncope among this age group and most of them recovered well after about five minutes.
The rate of syncope in this age group here is about 5.1 per 100,000 doses, which is similar to the rate from overseas reports, HSA said.
SERIOUS ADVERSE EVENTS
Of the 9,403 suspected adverse events, 389 — or 0.005 per cent of doses administered — were classified as “serious” adverse events.
This was on par with the 0.005 per cent that was recorded in the last safety update.
The most frequently reported ones were anaphylaxis (58 reports) and other severe allergic reactions (49 reports).
Others include:
- A worsening of an underlying asthma condition
- Breathing difficulty
- A fast heart rate
- An increase or decrease in blood pressure
- Chest discomfort and pain
- Myocarditis (heart inflammation)
- Pericarditis (inflammation of outer lining of the heart)
- Syncope
- Limb numbness, weakness or pain
- Changes in vision
- Increase in liver enzymes
- Thyroid gland dysfunction
- Muscle injury
- Joint pain
- Seizures (fits)
- Tinnitus (ringing in the ears)
- Blood clots
“These serious adverse events are being closely monitored by HSA. Background disease incidence or underlying medical conditions are taken into consideration when determining if the vaccine had any contributory role to these events.
“Most of the individuals who developed serious adverse events were reported to have recovered or are recovering,” the authority said.
ADVERSE EVENTS OF SPECIAL INTEREST
Anaphylaxis, Bell’s palsy, myocarditis and pericarditis are examples of adverse events of special interest, which is a “medically significant event that has been observed historically with other vaccines”.
1. Anaphylaxis
There were 58 cases of anaphylaxis reported with the Pfizer-BioNTech and Moderna vaccines, and all the patients were reported to have recovered after medical treatment.
Anaphylaxis is “a rare and potentially life-threatening allergic reaction that can occur following vaccination in certain susceptible individuals,” HSA said.
The incidence rate of anaphylaxis reported here with the vaccines is about 0.86 for every 100,000 doses administered and this is similar to the incidence rates reported overseas of around 0.5 to 2 for every 100,000 doses.
2. Myocarditis and pericarditis
There were also 34 reports here of myocarditis and pericarditis following more than seven million doses of vaccines administered.
Typical symptoms were chest pain, shortness of breath and a fast heartbeat.
Fourteen of these cases occurred in adults aged 30 and above, comprising eight men and six women.
The remaining 20 cases were among men below the age of 30.
“This has exceeded the expected numbers in this age group, based on the background incidence rates,” HSA noted.
Of the 34 cases, 15 were reported after the first dose of the mRNA vaccines and the remaining 19 were reported after the second dose.
HSA noted that most of the cases were reported to have occurred within one week of receiving the vaccine.
“Although there is a small increased risk of myocarditis and pericarditis, the local incidence rate remains low.
“The overall local incidence rate is 0.48 per 100,000 doses administered, and the incidence rate in males below 30 years old is 2.36 per 100,000 doses administered,” it said.
HSA stressed that it has not observed a greater frequency of heart attack and strokes in people who have been vaccinated in Singapore.
“Due to the large numbers of people being vaccinated, it is expected that, by coincidence, some individuals may experience other medical events such as heart attacks and strokes in the days or weeks after vaccination, which may not be related to the vaccination.”
3. Bell's palsy
As for Bell’s palsy, 66 cases have been reported, with most being non-serious.
Most of the patients will generally completely recover even without treatment, HSA said.
The local incidence rate is estimated to be 1.8 per 100,000 persons a month, which is within the background incidence of 1.1 to 4.4 per 100,000 persons a month before vaccination began.
4. Cerebral venous thrombosis
In addition, HSA noted that there have been “rare cases” of cerebral venous thrombosis reported with the mRNA vaccines both overseas and locally.
It is a rare type of blood clot that occurs in the veins of the brain and can “happen naturally regardless of whether people have been vaccinated or not”.
There were nine suspected reports of cerebral venous thrombosis with the Pfizer-BioNTech and Moderna vaccines.
“None of the cases had a fatal outcome. HSA is currently assessing the incidence rate of this adverse event against the background incidence rates.”
It added: “It is important to note that the cerebral venous thrombosis cases reported locally are not associated with thrombocytopenia (low platelet levels) and are different in clinical presentation from the overseas cases of cerebral venous thrombosis with thrombocytopenia that has been reported with the AstraZeneca and Janssen (Johnson & Johnson) Covid-19 vaccines.”
HSA said that its current assessment is that the benefits of the Pfizer-BioNTech and Moderna vaccines continue to outweigh the known risks of Covid-19.
“HSA and MOH (the Ministry of Health) will continue to monitor the safety profile of the Covid-19 vaccines closely, especially anaphylaxis, myocarditis and pericarditis risks, take the necessary regulatory actions, and update members of the public of any significant safety concerns detected with the vaccines.”
