A small study by the Indian Council for Medical Research (ICMR) has revealed that mixing Covishield and Covaxin is safe and yields better results.

Here is a quick look at the key points of the study:

• The study was conducted between May and June this year.

• It compared the reaction of 18 people who received two doses of two different vaccines by mistake in Uttar Pradesh, to 40 recipients of two doses of Covishield and 40 recipients of two doses of Covaxin.

• The study showed that the group of 18 people who got two different vaccines showed better immunogenicity.

• It is yet to be peer-reviewed.

Shortage of vaccine supplies has ramped up interest in mixing different COVID-19 vaccines and the scientific community is looking for answers across the world.

But the ICMR study was based on the goof-up that took place in Uttar Pradesh earlier this year, wherein a group of villagers were administered two doses of two separate vaccines.

"This is based on an unplanned and mistaken mixed administration of one dose each in UP. It makes immunological sense and is in line with what is seen with AZ-Pfizer dose mixing," Virologist Dr Shahid Jameel told FIT.

Eminent Immunologist Dr Satyajit Rath, the study reported in the pre-print is "too small, too unclearly written and has too many technical limitations."

Under the study titled ‘Serendipitous Covid-19 Vaccine-Mix in Uttar Pradesh, India: Safety and Immunogenicity Assessment of a Heterologous Regime’, 18 people received two doses of two different vaccines, the reaction of which was compared to 40 people who got two doses of Covishield and 40 recipients of two doses of Covaxin.

"Immunogenicity profile against Alpha, Beta and Delta variants in heterologous group was superior; IgG antibody and neutralising antibody response of the participants was also significantly higher compared to that in the homologous groups," it added.

The study was conducted between May and June this year.

The study said immunisation with a combination of an adenovirus vector platform-based vaccine, followed by inactivated whole virus vaccine was safe and elicited better immunogenicity.

But it's important to note that it is a very small study.

"The numbers in the ICMR analysis are still small but give reason to design larger trials," Dr Jameel told FIT.

"All statements, such as are being made based on it, regarding 'better immunity' with a Covishield+Covaxin regime, are therefore very premature in my view," Dr Rath added.

A group of villagers in Uttar Pradesh's Siddharthnagar district were given mixed doses of Covishield and Covaxin at a government hospital in May this year.

However, officials had claimed that no one faced any adverse health effects.

“We will have to wait for more scientific understanding of this for scrutiny and more understanding. But even if this has happened, it should not be a cause for concern for that individual,” Dr VK Paul, the Chair of NEGVAC (National Expert Group on Vaccine Administration for COVID-19), had said.

So, is mixing COVID-19 vaccines a good trend?

In May, experts had told FIT that there are no likely major concerns about the actual safety and side effects of the goof-up in UP.

However, they had cautioned against mixing of vaccines without proper studies.

Eminent Immunologist Dr Satyajit Rath, had called the goof-up and "awkward mix."

Dr Rakesh Mishra, former director and now advisor of the Center for Cellular and Molecular Biology (CCMB) had said, “Mixing of vaccines is normally not permitted. So, this is clearly a mistake. Simply because we don’t know about it’s efficacy."

Last month, a Subject Expert Committee of the Central Drugs Standard Control Organisation (CDSCO) recommended granting permission for trials on mixing Covishield and Covaxin vaccines.

In July, World Health Organisation chief scientist Soumya Swaminathan had advised against mixing and matching vaccines, and called it a "dangerous trend" since there was little data available.