Covid-19: Understanding heterologous and homologous boosters

With India nonetheless registering quite a few Covid instances, specialists are not sure whether or not or not the nation will face a fourth wave. The well being ministry recorded 3,205 new instances on May 3, displaying a 24.8 per cent spike in instances as in comparison with final month — making it extraordinarily important to get vaccinated, particularly amid XE variant. As such, Dr Haryax Pathak, a member of iCart, sheds gentle on heterologous and homologous boosters, and how they are often helpful within the battle in opposition to Covid.

Understanding heterologous and homologous boosters:

According to the professional, homologous boosters use the identical kind of vaccine as the primary and second doses. Citing an instance, he mentioned, “A person who got the first two doses of Covishield, a non-replicating viral vector, gets jabbed with the same.”

Heterologous boosters, then again, “use a different vaccine platform from the first couple of doses”. “A person who got two doses of Moderna (mRNA vaccine), would get jabbed with a different vaccine type such as Covaxin (Inactivated/Dead Virus) or Sputnik Light (Non-Replicating Viral Vector),” he defined.

“According to a study published by Lancet, homologous boosters increased neutralizing antibody titers by a factor of 4 to 20, whereas heterologous boosters increased titers by a factor of 6 to 73. For all clinical outcomes considered, heterologous boosters showed higher vaccine effectiveness than homologous boosters, providing an additional support for use of a mix-and-match approach,” he added.

According to Dr Pathak, “the current situation of heterologous boosters is still a work-in-progress in India. CMC Vellore, which was permitted to conduct homologous as well as heterologous booster dose trials by the national drugs regulator last year, is working on generating adequate data to be able to present before the subject experts of Central Drug Standard Control Organisation. The data, if approved, will then be presented before NTAGI that is already looking at scientific evidence in favour of recommending mix-and-match booster dose against Covid-19 to the health ministry.”

At the second, India has Covaxin together with Covishield and Sputnik Light vaccines obtainable.

vaccination, kids, children, news Booster is a precautionary dose to safeguard the inhabitants in opposition to a doable fourth wave. (Photo: Getty/Thinkstock)


The professional mentioned that Covishield utilises modified spike proteins from a chimpanzee adenovirus, ChAdOx1virus, to elicit immunity within the physique. During its booster trials, Covishield confirmed promising outcomes. When given as a booster shot, it elevated the immune response in opposition to Alpha, Beta, Delta, Gamma & Omicron SARS-CoV-2 variants.


“Covaxin is developed with Whole-Virion Inactivated Vero Cell-derived technology which means that it contains inactivated viruses that can not infect but give protection to a vaccinated person.”

According to the outcomes derived from a preliminary evaluation of an ongoing security and immunogenicity trial, 90 per cent of people, when boosted with Covaxin, had efficacy being maintained for a interval of six months. The boosted topics confirmed excessive neutralizing exercise in opposition to the Omicron variant as properly.


Dr Pathak additional mentioned Sputnik Light is predicated on recombinant human adenovirus (medium-sized, non enveloped) serotype quantity 26 (the primary part of Sputnik V). Based on information collected by the Spallanzani Institute and outcomes of earlier research, heterologous boosting with Sputnik Light tends to extend the efficacy of different vaccines and prolong the booster safety interval as optimum adenoviral platform configuration supplies higher safety in opposition to Omicron and different variants.

Explaining the significance of a booster dose, the professional mentioned, “The government has announced free administration of a third booster dose due to the rapid increase in the number of Covid cases and emergence of new variants. It is a precautionary dose to safeguard the population against a possible fourth wave. While it is still not mandatory to get a booster dose, those eligible must get it. This ensures protection against infection and even higher protection against severe symptoms or hospitalisation.”

As per a research by JAMA, full vaccination, with booster/precaution dose can also be recognized to cut back transmission of an infection to some extent, which coupled with correct masking and distancing is crucial in stopping the additional emergence of latest variants.

“It is important for the government to look at the data for mix and match boosting as is being done in most other countries. Let’s make sure we get through this pandemic safely together,” the professional mentioned.

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