Vaccine boosters could have a dual positive impact on the Covid-19 pandemic. They can boost the immune response against the original SARS-CoV-2 virus, as well as provide methods to overcome the emerging viral variants that could render existing vaccines ineffective. Looking ahead, how can these boosters be distributed to ensure they are used most effectively to tackle the health crisis?

Like most infectious pathogens, SARS-CoV-2, the coronavirus that causes Covid-19, is mutating,  causing new variants to emerge. This is part of the virus’s evolutionary mechanism to help it evade the immune system. However, it is creating concerns that Covid-19 vaccines – the main global exit strategy out of the pandemic – may become ineffective at helping the immune system fight SARS-CoV-2, putting the world back at square one.

To date, three main variants have been detected in various countries around the world. The first was identified in Kent, the UK, and is known as B117. The second is known as the South African variant or B1351, while the third emerged in Manaus, Brazil, and is called P1.

Studies have suggested that the two approved mRNA vaccines – BNT162b2 produced by Pfizer and BioNTech, and mRNA-1273 by Moderna – have managed to neutralise both the UK and South African variants. AstraZeneca’s Covid-19 vaccine, ChAdOx1 nCoV-19, which was developed in collaboration with the University of Oxford, however, provided minimal protection against the more worrying South African variant.

A laboratory study carried out by the University of Texas found that Pfizer/BioNTech’s BNT162b2 vaccine could neutralise the highly contagious Brazilian P1 variant. Other studies are underway to figure out if the other two UK-approved vaccines are effective against this newer variant.

The solution: vaccine boosters focused on variants

Although so far both Pfizer/BioNTech and Moderna’s mRNA vaccines have been found to be effective against the concerning South African variant, B1351, the companies both decided they need to be prepared for the future of the Covid-19 crisis by developing vaccine boosters.

In addition, as AstraZeneca/University of Oxford’s vaccine elicited substantially reduced viral neutralisation against B1351, compared to the original Covid-19 strain, the partners also decided to develop a variant booster.

“Vaccine boosters can help tackle the threat of emerging variants by providing individuals [with] immunity against known variants,” explains Albany College of Pharmacy and Health Sciences associate professor of microbiology Dr Eric Yager. “Boosters have been used successfully with seasonal flu vaccines. Receiving the flu vaccine each year can work like a booster to enhance immunity against that flu strain.”

In addition, Yager explains that “by reducing the number of people infected with the original virus and those infected with the variants, we can reduce the occurrence of additional variants”. This is because variants are created in people infected with Covid-19, and “fewer infected people means fewer opportunities for the virus to mutate, which in turn means fewer future variants”.