Mix-and-match vaccination is safe say the PM and experts

Younten Tshedup  

To boost public confidence Prime Minister Dr Lotay Tshering will receive the Moderna vaccine as his booster dose at 9am today.

This would be three days ahead of the scheduled second mass vaccination campaign which starts from July 20. Lyonchhen will receive the Moderna vaccine along with a group of volunteers at the RBP flu clinic in Thimphu. He was the second person to receive the Covishield vaccine (AstraZeneca) on March 27, earlier this year.

In a news release posted on social media, the Prime Minister was quoted saying, “In addition to my professional understanding and scientific data, this will help me share my personal experience with you all.”

Lyonchhen announced the government’s plan, in his office’s Facebook page, to go ahead with the Moderna vaccine as the second dose for those who received AstraZeneca as the first dose. However, he said that AstraZeneca doses will also be made available as the second dose for those who insist on it for personal reasons.

Lyonchhen, in the Facebook post yesterday, said that all the Covid-19 vaccines that have received emergency use approval (EUA) were safe. Bhutan currently has four different types of vaccines at its disposal — AstraZeneca, Moderna, Pfizer, and Sinopharm — which are all WHO EUA approved.

However, he said that on the protection from the vaccines there was growing literature indicating better immune response in people who received mRNA (Moderna or Pfizer) as their second dose to AstraZeneca as their first dose.

He explained that while the heterologous regimen (mixing of vaccines) produced better immune response, it did not mean the homologous mode (same vaccine for two doses) of vaccination were ineffective. “It is also valid to have same vaccine for the second dose.”

Given the sufficient doses the country had, Lyonchhen said first-timers can receive either AstraZeneca, Sinopharm or Moderna vaccines and for this group of people, the second dose could be Moderna and Sinopharm vaccines in four weeks later or AstraZeneca between 12 to 16 weeks in homologous mode.

Heterologous options would also be provided based on availability, he added.

The country has secured approximately 965,850 doses of various types of Covid-19 vaccines including 60,000 plus extra doses of AstraZeneca vaccines from the first round.

The Prime Minister also said that the limited number of Pfizer vaccines (5,850 doses) would be used to cover children between 12 and 17 years in high-risk areas of Phuentsholing and Samtse. The vaccines would also be used for those travelling outside for treatment and studies.

“While studies are underway, we are also waiting for evidence to emerge in the coming days for use of Moderna in children below 17 years, for which works are already underway to ensure timely vaccination,” he added.

Mix-and-match is safe   

There is growing evidence that mixing of Covid-19 vaccines was not only effective in triggering a robust immune response against the Delta variant of SARS-CoV-2 virus but it was also found that the side effects were almost the same as in the homologous approach, if not less.

Of the many, three studies conducted in the United Kingdom, Spain, and Germany found that mixing of AstraZeneca vaccines with a mRNA vaccine produced significant increase in the immune response in people.

People aged 18 to 69 participated in the clinical trials for the studies. It was also found that there were only mild to moderate side effects including headache, fever, joint pain, and pain at the site of injection. No major AEFI (adverse event following immunisation) were reported in any of the studies.

Technically, mixing of different vaccines has been happening for a long time now. The same heterologous approach is used in vaccines for malaria, tuberculosis, Ebola, and some cancer therapy.

Some experts said that all the EUA approved vaccines for Covid-19 were made keeping in mind the initial strain of the SARS-CoV-2 virus detected in Wuhan, China. “No doubt the vaccines are still effective today. However, the efficacy of these vaccines reduces when it has to fight new mutants like the Alpha, Beta, or the Delta variants,” said an expert. “This is why the mix-and-match regimen is picking up in many developed countries where multiple variants of the virus have been reported.”

Lyonchhen said that people must consider getting vaccinated first rather than exploring the choice of vaccines. He said that the Delta variant of SARS-CoV-2 virus was more contagious which was why a high vaccine coverage was required to achieve herd immunity.

“We need to vaccinate an arbitrary minimum of 80 percent of the total population, in the shortest possible time. This will give us the much-desired opportunity to reduce Covid-19 from the public health hazard status to an individual health problem,” he said.

Lyonchhen said that vaccination, and subsequently herd immunity, was the only way to enter the ‘new normal’ era sooner. “However, as we consider post-vaccination protocols, the same restrictions will continue to be imposed on those who are not vaccinated, given the risk they pose to themselves or others.”