Malaysian medical experts: No evidence to show mixing Covid-19 vaccines harmful, booster shots still safest way to protect yourself

·5-min read
A woman receives her Covid-19 booster shot at the Perak Community Specialist Hospital in Ipoh January 3, 2022. — Picture by Farhan Najib
A woman receives her Covid-19 booster shot at the Perak Community Specialist Hospital in Ipoh January 3, 2022. — Picture by Farhan Najib

KUALA LUMPUR, Jan 4 — Two years into the Covid-19 pandemic and with 78 per cent of the total population fully vaccinated, there was still hesitancy about booster jabs when it was first rolled out last October.

A high number of people with appointments simply did not turn up.

Many were afraid of mixing vaccines even though medical experts say there is absolutely no reason for the mistrust, especially for those who have been administered Sinovac jabs.

They say there isn’t enough evidence to suggest that mixing vaccines can have an adverse effect, with the current recommendation of two doses of the Sinovac vaccine followed by a Pfizer booster shot still the most viable option to stay immunised from the SARS-CoV-2 virus.

Homologous booster shots refer to the same vaccine type being given to a person who has been fully vaccinated (two Pfizer shots followed by another Pfizer booster jab, for example) whereas heterologous or “mix and match” booster shots refer to when a different vaccine is given (two Sinovac shots followed by a Pfizer booster shot, for example).

Respiratory specialist Dr Helmy Haja Mydin said studies conducted in Europe and published in scientific journal Nature showed that those with mixed vaccines were 68 per cent less likely to develop symptomatic infections compared to 50 per cent for homologous booster recipients.

Dr Helmy said there is a need to continue educating people to allay their fears as we could be on the brink of another outbreak.

“Repeated messages should be sent addressing doubts and it is worth noting the adverse reactions are not higher when vaccines are mixed.

“The World Health Organisation (WHO) regional director Hans Kluge said there could be half a million deaths in Europe by the first quarter of this year if they did not return to the way they were by wearing masks and increasing vaccine uptake,” he added.

Booster shots were administered nationwide starting October 13 for fully vaccinated individuals as well as for senior citizens aged 60 and above and frontliners who have completed vaccination after six months.

Health Minister Khairy Jamaluddin said he was aware of a foreign study that found two doses of Sinovac’s Covid-19 vaccine followed by a booster Pfizer-BioNTech shot producing a lower immune response against the Omicron variant compared with other variants.

He was asked if recipients of the Sinovac vaccine who received the Pfizer booster shot in Malaysia may require a fourth dose in the future, to which he said the matter was still being studied.

Khairy said the Health Ministry’s technical team will be proposing recommendations to the Covid-19 Immunization Task Force (CITF) after completing a few studies of its own, adding that it was still too early to draw any definite conclusions.

A report cited by Reuters yesterday said the Sinovac two-dose regime, along with the Pfizer booster shot, produced an antibody response similar to a two-dose mRNA vaccine like Pfizer and Moderna.

The study, which has not been peer-reviewed yet, was conducted by researchers from Yale University, the Dominican Republic’s Ministry of Health and other institutions.

Public Health Medicine Specialist and Professor of Epidemiology at the Department of Social and Preventive Medicine, Faculty of Medicine, University of Malaya Dr Sanjay Rampal agreed with Dr Helmy that the pushback against heterologous shots is unsubstantiated.

“Those who have gotten two previous Sinovac shots should be encouraged to get a Pfizer booster. However, there is resistance from certain parts of the community that still only prefer Sinovac, a likely result of either trusting the reported effects of Sinovac or distrusting Pfizer.

“Grassroots leaders have to be engaged to view the evidence objectively and promote better vaccines. A lot of Sinovac vaccines have also been purchased. A moratorium on further purchases may be indicated pending more complete evidence-based reports,” he said.

Dr Nirmala Bhoo Pathy, a Public Health Medicine Specialist and Associate Professor of Epidemiology at the Department of Social and Preventive Medicine, Faculty of Medicine, University of Malaya also agreed.

She pointed out that the Health Ministry had recommended Pfizer booster shots, with Sinovac only to be admininistered as booster shots for individuals who cannot take the Pfizer vaccine due to medical reasons.

She said present evidence still suggests that booster shots help protect against the Omicron variant.

“To date, there has been no evidence of serious adverse events from populations who received heterologous (mixed) vaccines from other parts of the world.

“So, this should serve as a reassurance that it’s okay to receive Sino-Sino-Pfizer,” she said.

However, the initial booster hesitancy among older Malaysians seems to have been overtaken by younger Malaysians eager for their booster shots.

Over the weekend, long queues formed at several malls around Klang Valley where booster shots were being given.

Paradigm Mall in Kelana Jaya, iHeal Medical Centre in Kuala Lumpur and Subang Parade PPV were among the areas where large crowds had gathered for walk-in booster shots.

This was a result of Putrajaya shortening the interval period for all Covid-19 vaccine recipients to three months.

Coupled with the recent floods in Kelantan, Pahang, Johor, Negri Sembilan, Kuala Lumpur and Selangor which caused some clusters to emerge at the temporary relief centres, Malaysians are choosing to protect themselves.

As the country enters the endemic phase and international borders are set to reopen to foreign travellers, the need to be immunised is even greater as more virulent strains of the coronavirus appear.

“In the end, everything we do is to mitigate risk. Wearing masks, avoiding crowded spaces and getting vaccinated are not guarantees to prevent contracting the virus,” said Dr Helmy.

“What we cannot argue with is the fact that the pandemic is deadly to those who cannot mount an appropriate immune response.”

Malaysia has reported 64 cases of the Omicron variant as of December 31, 2021.

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