MIXING Covid-19 vaccines is not encouraged presently, let alone for booster shots or for the primary intake of two doses, vaccine specialist Dr Ajith Pal Singh said today. 

Ajith, who is the head of biology and vaccine specialist at Pharmaniaga Bhd, said present scientific studies show that mixing Covid-19 vaccines could cause one to experience greater side effects compared to receiving one type of vaccine. 

“The well-designed study in the United Kingdom, which is being done on the mixing of Covid-19 vaccines, is not only for boosters but also on primary (shots) in the UK. It has demonstrated that when a vaccine is mixed – ‘A’ and ‘B’ – the side effects are different then when you give ‘A’ and ‘A’ or ‘B’ and ‘B’. 

“In some of the cases, when you mix vaccine ‘A’ and ‘B’, the side effects are much higher than the cumulative of two different mixes compared to vaccine ‘A’ and ‘A’ only,” he said in a webinar titled Covid-19 Booster Shots and Vaccination for Children. 

Ajit, however, did not name the type of vaccines in the UK study as the data are still under review. 

Recently, Health Minister Khairy Jamaluddin told the Dewan Rakyat that a heterologous “mix and match” approach would be taken for those eligible for booster vaccine shots.

Ajit said one should not attempt to mix any type of Covid-19 vaccines and that it has to be scientifically proven to be safe before it is done. 

He expressed his concern over the matter due to a lack of reliable data and cited a recent case in Thailand that led to the death of a vaccine recipient.

In Thailand, a 39-year-old man died a week after he received a second Covid-19 shot, with a different vaccine – a Sinovac jab for the first and AstraZeneca the second. 

An investigation has been launched into his death. 

Ajit said that data on mixing vaccines are evolving. However, he cautioned that there are risks involved.

“It is risky. It is not demonstrated what could be the long-term and short-term side effects.

“As of now, the data are still evolving. We don’t know how risky it would be,” he said. 

Ajit acknowledged that several countries have started mixing vaccines but said that it was done due to three reasons – inadequate supply of vaccines, side effects of a particular vaccine, and also the cost of vaccines. 

As of yesterday, Malaysia had fully vaccinated 21.6 million or 66.1% of the general population. 

Of them, 21.2 million are adults. – October 13, 2021.