MIXING and matching different types of vaccines, or heterologous vaccination, for booster shots is safe and has been proven to be effective, health experts said amid growing concern that Malaysians are refusing to take the third dose, fearing adverse effects.

Health Minister Khairy Jamaluddin had said that 40% of those who received appointments for their booster shot failed to turn up. He warned that these people could land in hospital with severe illness linked to Covid-19.

The Health Ministry also said the Pfizer and AstraZeneca vaccines are recommended as booster shots for all types of primary shots.

People receiving Sinovac as their primary shot have Pfizer AstraZeneca and Sinovac as available options.

Professor of epidemiology at the Department of Social and Preventive Medicine, Faculty of Medicine, Universiti Malaya, Moy Foong Ming recommended Pfizer or AstraZeneca as booster shots for Sinovac recipients as the combination is more effective than homologous vaccination, where the same vaccine as the primary shot is used.

“When you mix (with Pfizer or AstraZeneca) the effectiveness is 95%. When you take the same vaccine for Sinovac, it is only 75%,” she told The Malaysian Insight.

“Even in Singapore, they have encouraged their citizens to mix with Pfizer rather than taking Sinovac,” Moy said.

She added that – based on data from Indonesia, Cambodia, Thailand, Singapore and Western countries – no severe effects have been reported from heterologous vaccination.

“From the data received, it showed that mixing of vaccines gives higher effectiveness,” she said.

She suggested Sinovac as a booster shot for people unable to take mRNA vaccines. However, Moy advised recipients to accept the vaccines offered to them regardless of the make.

“The effectiveness of the third Pfizer or AstraZeneca dose is very good, not like Sinovac, which has an effectiveness of 75%,” she said when asked about the options for those who were inoculated by one of the two vaccines.

Former deputy health minister Dr Lee Boon Chye said people should be given the chance to choose their preferred booster shots as they, including Sinovac, seem to work.

“So, I think now that the Sinovac vaccine is approved as a booster shot, this would be good because it gives the people a choice.

“Even though the data from Chile, where Pfizer is marginally better than Sinovac, it is still data taken in the short term.

“People are still concerned about long-term mRNA vaccine effects, which nobody can guarantee,” he said.

“I received the Pfizer vaccine, so it is not a problem but you must give people the choice. After all, the booster vaccines seem to work, even Sinovac. So, why stop people from making their choice?” he added.

Azrul Mohd Khalib, who is the head of the Galen Centre for Health and Social Policy said the recommendation for heterologous vaccination is based on science and data.

“We don’t simply copy and paste protocols from the US, for example, as they don’t use Sinovac, whereas a large proportion of the population here is inoculated with that vaccine.

“We have to look to studies which mix and match using that vaccine,” he said.

“Based on what we know so far, heterologous inoculation using the mRNA vaccine is the way to go, as it seems to offer significantly increased protection as a booster based on what we have seen in other countries so far.

“It addresses the issue of waning immunity, particularly among those inoculated with Sinovac, and increases the level of protection for the recipient,” he added.

President of the Malaysian Medical Association (MMA) Dr Koh Kar Chai said the health ministry has given assurance about the efficacy and safety of approved heterologous boosters based on evidence.

“It had also given its recommendations on who should get the booster jabs. Based on current available evidence, the booster shots are safe and proven to increase protection against Covid-19,” he added.

Why are people missing appointments?

Moy noted that much of the “unfounded” anxiety and fear over booster shots and heterologous vaccination could have stemmed from misinformation that was doing the rounds on social media.

Lee, on the other hand, said misinformation will continue to exist but it is important for the government to be transparent about the data and explain to the people about booster shots to build trust.

“The data should have been communicated much sooner. For example, they should have said something about the waning effect of the Sinovac vaccine after three months long before now.

“Sinovac vaccine recipients should have been given the option to get the booster much earlier rather than concealing the information and letting them know at the last minute. So, all this should have been transparent,” Lee said.

“There are things we don’t know. If you don’t know, just admit it and say we have no information on it as yet and are waiting for new information to come in,” he added.

Lee noted that there was lack of publicity on booster shots from the Health Ministry.

“I know a lot of people who have received appointments but then by the time they realise it, the appointments have already passed.

“There is no mechanism for those who have missed their appointments to go and get their booster shots again (until recently where walk-ins were allowed).

“There was nothing arranged as soon as possible,” he said.

However, Koh noted that some people may have given their appointments a miss because they were not convinced that it was necessary after completing their original inoculation, while others may be concerned over heterologous vaccination.

He said people derive information from multiple sources and there are different views. This, he said, is enough to create doubts and lead to a certain degree of hesitancy.

Universiti Putra Malaysia medical epidemiologist Associate Prof Dr Malina Osman said some may simply be complacent, while others may have missed their appointments because they wanted to take a wait-and-see approach.

“Misinformation may also be a reason, but I think the real issue is due to concerns of limited clinical data to support the heterologous vaccinations.

“However, based on current findings, more and more studies show that heterologous vaccines are safe and effective,” she said.

Meanwhile, Azrul said that there is a lack of discussion on the merits of heterologous booster vaccination and also a clear understanding of its urgency.

“People are a bit in the dark, including healthcare professionals. The Ministry of Health has started to do this (talk up booster shots), especially the minister, but the damage caused by misinformation and disinformation has been quite far-reaching,” he said.

He said anti-vaxxer groups have taken advantage to increase hesitancy about this issue, and have been sowing doubt and suspicion among people who have already completed their vaccination. – November 26, 2021.