Health

Continued surveillance can help tweak vaccines for COVID-19 variants

Need to seamlessly connect vaccine development pipelines to variant identification and testing so that time can be saved while updating vaccines for newer variants, experts say

 
By Vibha Varshney
Published: Friday 25 June 2021

As variants of SARS-CoV-2 that cause the novel coronavirus disease (COVID-19) continue to emerge, it is feared that these could derail global vaccination efforts by rendering the existing vaccines ineffective. Now, researchers in the United States have stated that studying ‘breakthrough infections’, which occur after vaccination, could provide intelligence to fight new variants.

Researchers from the University of Washington studied 20 vaccine breakthrough cases. They reported in the journal Clinical Infectious Diseases on June 24, 2021 that all the infections were due to variants of concern (VoCs). 

They suggested that continued surveillance of such breakthrough cases might help target VoCs for inclusion in new or booster SARS-CoV-2 vaccines.

Viral mutation

Much can be said about the way a virus mutates but the crux of the matter is that it mutates easily. As it spreads among vulnerable populations, it changes. Other than the changes due to natural causes, it can also change due to selection pressure from vaccines and treatments used in sick people. 

Such changes can be both good and bad. However, in the case of SARS-CoV-2 that causes COVID-19, the changes have made the virus stronger and are being called VoCs. The latest variants transmit more easily and can evade the body’s immune system.

In India, the latest data on VoCs shared by the government on June 25 shows that these increased from around 10 per cent in January to more than 50 per cent in June.   

“Variants that partially evade immune responses are able to cause re-infections and breakthrough infection. All this makes it harder to control the pandemic,” Shahid Jameel, director, Trivedi School of Biosciences, Ashoka University in Haryana, told Down To Earth (DTE).

Balram Bhargava, director-general of the Indian Council of Medical Research, shared data on the reduction of neutralisation capacity of different vaccines globally.

This showed that the efficacy of Covaxin, manufactured by Bharat Biotech Intl Ltd was not affected against the alpha variant but in case of the delta variant, there was a 3-fold reduction. While Covishield, manufactured by AstraZeneca plc showed a 2.5 fold reduction in neutralisation capacity against the alpha variant, there was only a 2 fold reduction in case of the delta variant. Vaccines like those made by Pfizer plc and Moderna, Inc showed a 7-fold reduction in efficacy. 

The researchers are not concerned about these changes as of now but it is quite likely that soon, there would be a need to update vaccines based on surveillance data of the circulating variant.

Such variants are the reason that the flu vaccine has to be tweaked every year to be able to protect people from the latest variant. 

Mutation and selection are low frequency events and variant viruses are generated and appear in the population only when low frequency is compensated by a high number of infections. This is the reason why viruses like Japanese Encephalitis and Nipah usually fail to cause pandemics.

The efficacy of COVID-19 vaccines could fall anytime and researchers emphasise on regular surveillance to identify VoCs. This is expensive and difficult to carry out in poor countries. But new strategies can help. 

Updating vaccines

If vaccines need to be updated regularly, messenger Ribonucleic Acid or mRNA vaccines are likely to be easier to manipulate as the genetic material being used to trigger immunity can be quickly changed. 

Vectored vaccines like those manufactured by AstraZeneca plc would require that the new variant’s sequence is inserted in the vector. 

In both cases, the developers can also include both, new and old genetic material, in a single jab to make a multivalent vaccine. However, the whole virus vaccine provides a wider immunity and might continue to be effective against variants. But studies are needed. 

In all cases, the modified vaccine might need to go through the process of clinical trials again. This does not happen in the case of influenza virus so far but then, the science of flu vaccine is more established. 

There is a need to seamlessly connect the vaccine development pipelines to this variant identification and testing process so that next-generation vaccine development against such variants of substantive concern can start without downtime, Satyajit Rath, immunologist and visiting professor at IISER Pune, said

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