SINGAPORE - The Covid-19 mRNA vaccines by Pfizer-BioNTech and Moderna may have a likely link to heart problems but these events remain rare, with the benefits of immunisation greatly outweighing the risks.
Most recently, a 16-year-old boy collapsed after strenuous exertion six days following his first dose of the vaccine. Investigations are ongoing to determine the cause of his cardiac arrest and it remains unclear if the incident was linked to his vaccination.
As at June 30, Singapore's Health Sciences Authority (HSA) received 12 reports of myocarditis and pericarditis occurring in people following their vaccinations with mRNA Covid-19 vaccines.
The risk of such heart inflammations appears to be higher after the second dose of an mRNA vaccine than the first, and higher in men than women.
Incidents of heart problems have also been reported abroad. More than 1,200 Americans, including about 500 who were younger than age 30, reported symptoms after their mRNA jabs, according to data reported in late June by the United States Centres for Disease Control and Prevention (CDC).
Most cases were mild, CDC researchers said. Of the 484 cases reported in Americans under the age of 30, 323 cases were definitively linked to vaccination. The rest remain under investigation.
Why it matters
Bad news is often quick to dominate the headlines and may breed fear and hesitancy among those who are contemplating taking the vaccine.
Yet, a deeper look at the data will illustrate that vaccine benefits continue to hugely outweigh its risks.
Despite these unfortunate incidents, experts said it still makes good sense - and remains mathematically logical - for young people to get inoculated. This is even though the young have a lower risk of developing severe Covid-19 disease should they get infected.
With Covid-19 due to become endemic and as countries gradually start to reopen their borders, the decision on vaccination is not a choice between the vaccine and nothing, but rather, between the vaccine and the risk of developing Covid-19 disease and its associated complications, said Professor Dale Fisher, a senior infectious diseases consultant at the National University Hospital.
The world is still learning about complications, such as long Covid-19, in which symptoms like fatigue and chest pains linger for weeks and months after infection. With more variants emerging, it also becomes more critical that both doses are taken to achieve better protection.
"There is no doubt that it's safer to have the vaccine than the disease. Covid-19 is not going away," Prof Fisher said.
So far, the science has also shown that the immune response generated from mRNA vaccines is superior to that from other vaccine types.
In an article published on June 28 in the scientific journal Nature, scientists found that a persistent immune response set off by the Pfizer-BioNTech and Moderna jabs potentially protects a person against the virus for years if the variants do not evolve much beyond their current forms.
These two mRNA vaccines have shown to be more than 90 per cent efficacious against the original strain and roughly over 60 per cent effective against the more transmissible Delta strain.
What lies ahead
Guidelines have now been issued to mitigate the risks of vaccine-induced heart inflammation to make vaccination safer for everyone.
Swimming, cycling, lifting heavy weights, as well as ball and racket games are some of the activities individuals should avoid for seven days after receiving their first and second Covid-19 jabs, the Ministry of Health said.
They should also take a break from competitive sports and physical education classes, which are considered strenuous. Physical activities that are safe include casual walking, stretching, working while standing and housework.
Students in schools and institutes of higher learning will be excused from physical activity for a week after receiving their first and second jabs.
Globally, as more data emerges and research continues in the months ahead, a clearer picture of what happens could then be pieced together.