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Should you mix and match Covid-19 vaccines for your booster shot?

Are you getting a Covid-19 booster dose and aren't sure if you should mix vaccines? "For the booster shots, we have more than enough proof of their safety. While side effects like arm soreness, exhaustion, and fever are to be expected, choosing to remain with the same vaccination or switch to a new one is more a matter of personal opinion."

In the United States, patients who are eligible for boosters can get any licensed Covid-19 vaccination, regardless of which one they got before.

Kenneth Mak, head of medical services at the Ministry of Health, informed the public that getting a different mRNA vaccination as a booster dose is "absolutely safe."


Associate Professor Mak confessed that he had added the Moderna vaccine to his two doses of the Pfizer BioNTech/Comirnaty vaccine for his booster shot, partially out of convenience. Health Minister Ong Ye Kung stated he, too, had taken Moderna as a booster following prior Pfizer BioNTech/Comirnaty shots at the same multi-ministerial task group on Covid-19 news conference.


Cheryl Low, 32, a business development professional, chose Moderna as a booster after her Pfizer vaccinations because she had heard the previous vaccine had a greater effectiveness rate.


She claims that the two-day fever and body soreness she had after taking the Moderna booster were comparable to the adverse effects she experienced after taking her second Pfizer dose.


Taking Moderna as a booster resulted in increased levels of antibodies, which is one sign of improved protection, according to a research conducted in the United States.


In the United States, patients who are eligible for boosters can get any licensed Covid-19 vaccination, regardless of which one they got before. This implies they can have a Pfizer, Moderna, or Johnson & Johnson booster injection.


The early research by the National Institutes of Health (NIH) looked at how 458 persons who had been vaccinated with Moderna, Pfizer, or Johnson & Johnson reacted to a booster dose of the same shot or a new one.


Antibody levels were observed to be greatest in those who had received the Moderna vaccination for the first two doses and the Moderna booster. The second highest antibody level was among those who had two Pfizer dosages followed by a Moderna booster.


However, Singapore physicians advise The Straits Times that choosing between the two mRNA vaccines - Moderna and Pfizer BioNTech/Comirnaty - makes little difference in terms of booster effectiveness.


According to the NIH study, there is evidence of equal effectiveness and immunogenicity with either Pfizer BioNTech/Comirnaty or Moderna vaccines as boosters, according to Dr. Alvin Neo, chief of clinical initiatives at clinic chain Northeast Medical Group.


Immunogenicity refers to a cell's or tissue's ability to elicit an immune response.


"The increase in immune response with the various mRNA vaccines is not particularly large," adds Dr. Neo, "and may not reflect a considerable incremental protection rate."

He goes on to say that, in order to maximize protection, it's probably best to obtain the most easily accessible authorized vaccine as soon as feasible.


"The reality is that both the mRNA vaccines perform effectively as boosters and may be given in any combination," explains Dr. Leong Choon Kit, a family physician at Mission Medical Clinic.


Aside from individuals who combine mRNA vaccinations, some people pick a non-mRNA vaccine like Sinovac or Sinopharm as a booster since they experienced negative side effects from mRNA vaccines.


Kenneth Loh, a massage therapist, received a Sinovac booster after experiencing fever and diarrhoea for a few days following his second Moderna vaccine.


"I didn't want to go through the same trauma," the 35-year-old says, "so I thought I'd take a less powerful shot to be safe."

The booster jab left him with simply a sore arm.


However, if a person has had an mRNA vaccination, Dr William Tan, a resident doctor at Doctors Express Medical Clinic in Raffles Place, advises that he continue with an mRNA type vaccine for the booster dose.


People with myocarditis (heart inflammation) or a history of high-risk allergic responses, such as trouble breathing, are an exception, he says. "The alternative will be a non-mRNA vaccination like Sinovac," he says.


There are no published research on the effect of taking Sinovac or Sinopharm as a booster following mRNA immunization, according to Associate Professor Hsu Li Yang, an infectious diseases expert at the National University of Singapore Saw Swee Hock School of Public Health.

"Although I suspect that, in general, the levels of antibodies post-booster may not be as high as if the individuals had received an mRNA vaccine as a booster," he says, "I suspect that, in general, the levels of antibodies post-booster may not be as high as if the individuals had received an mRNA vaccine as a booster."

Prof Hsu advises against playing it safe and sticking to the same vaccination for booster injections: "For the booster shots, we have more than enough proof of their safety. While side effects like arm soreness, exhaustion, and fever are to be expected, choosing to remain with the same vaccination or switch to a new one is more a matter of personal opinion."


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