There are two types of vaccines for coronavirus namely the inactivated one that is an old technology and the second type is the mRNA vaccine that is manufactured by a new technology. While the first one remains outside human cells and triggers antibody formation, the second one enters the body cells, becomes part of them and then trains the body to synthesize antibodies. Many people are hesitant to have the second type of vaccine though they are comfortable with the first one and prefer it.
When 32-year-old Jade Lim, a vet from Singapore opted for Sinovac-Coronavac (the inactivated vivid vaccine) instead of Pfizer or Moderna vaccine (mRNA vaccine), her friends and relatives could not believe. She says:
“As a healthy person with a good immune system, I feel that it wasn’t necessary to take something that would trigger so much reaction in the body,”
“Also … what’ll happen 50 years later (is something) we wouldn’t know, whereas inactivated virus (vaccines) have been used for decades.”
One cannot disagree with her line of thinking. The inactivated technology has been in use in vaccine production since the end of the 19th century and known to have no long-term issues. But mRNA technology is just over one decade old having started in 2009. The long-term consequences of injecting viral genetic code into the body are yet unknown. Hence this explains people's unwillingness to go for mRNA vaccines for covid.
Glutinous or sticky rice
What experts say?
There are some infectious diseases experts as well as former Pfizer company scientists who are with the people's voice and feel that immune response with mRNA vaccines for covid is unpredictable. Hence it could have both short term as well as long term issues in some. But there are others who do not agree. Infectious diseases specialist Loh Jiashen from Farrer Park Hospital states:
“The amount of (mRNA) data that’s come back has been rigorous, robust, and the whole data has been examined under the microscope,” he said. “The Sinovac safety data isn’t as open and not as publicly available.”
He also feels that Sinovac is less effective. Loh adds:
“If you want to give a vaccine, you should generate antibodies at least better or more than somebody who’s caught an infection,” he added.
“In its early trial, it was shown that the antibody (level) generated by the Sinovac vaccine was lower than that generated by people who’ve gotten COVID.”
But newer studies also reveal that both Pfizer and Moderna vaccines have diminished efficacy against delta mutant of the virus. Also despite above 75% vaccination rate in the UK with double dose of Pfizer or Moderna vaccine, cases of corona have not dropped.
David Lam from Hong Kong says:
“The efficacy of preventing hospitalisation and preventing death is very similar for both vaccines, so the efficacious advantage for (Pfizer-)BioNTech isn’t that obvious,” (NEJM study).
He adds that mRNA vaccines give more pains. Therefore, with equal efficacy and less adverse effects, people prefer to go for Sinovac. 28 cases of Bell's palsy were supposedly linked to Sinovac vaccine. But there is no definite evidence of this link. In Hong Kong, both vaccines are covered for adverse eventuality.
Some countries advise Pfizer or Moderna booster jabs to those who got Sinovac vaccine two doses. The take home message is to have some covid vaccine rather than not.
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