Does updating COVID-19 vaccines frequently have any benefits?

Subject: Science and Tech

Section: Health

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Researchers update the composition of influenza vaccines every six months to match the strains of the virus that are circulating in the wild, so that the shots may provide protective immunity against the flu.
But despite their best efforts, researchers rarely perfectly match the strains loaded in the vaccine with the strains circulating by the time the vaccines reach the market.
The reason for this is the long gestation period usually at least six months between identifying the circulating strain and the development, manufacturing, and distribution of the vaccines.
By the time the updated flu vaccine is available, the circulating strain may have drifted from the one contained in the vaccine, thanks to the high mutational rates of influenza viruses.
The Omicron variant, with its antigenic distance, has further complicated vaccine efficacy. Despite efforts to update vaccines, newer variants like XBB.1.5 and JN.1 present hurdles. Studies suggest updating vaccines may enhance neutralizing antibody titers against future variants, but uncertainties persist about long-term efficacy and T-cell immunity. India, with its Corbevax and Gemcovac vaccines, faces decisions on updating formulations to counter emerging variants.

Virus Variant:

Variants of a virus have one or more mutations that differentiate it from the other variants that are in circulation. While most mutations are deleterious for the virus, some make it easier for the virus to survive.
The SARS-CoV-2 (Corona) virus is evolving fast because of the scale at which it has infected people around the world. High levels of circulation mean it is easier for the virus to change as it is able to replicate faster.
The original pandemic virus (founder variant) was Wu.Hu.1 (Wuhan virus). In a few months, variant D614G emerged and became globally dominant.

Concerns Related to Different Variants:

Increased Transmission:
- In many countries, including India, variants, by virtue of increased transmissibility, have kicked off new wave(s) of epidemic transmission.
Increased Severity:
- Regarding virulence (propensity to cause severe/life-threatening disease), the UK variant is worse. The South Africa and Brazil variants do not seem to have higher virulence.
Lowered Immunity:
- The third concern is regarding the immunity cover offered by vaccination using antigens made from the D614G variant — which applies to most vaccines in current use.
- Lowered efficacy of vaccines was found more with the South African and less with the Brazil variant. Hence, reinfection can occur in spite of immunity by earlier D614G infection or vaccination.
- Vaccine efficacy may be lower now than what was determined in phase-3 trials as VOC were not then widely prevalent.