Will India need a booster dose to fight new variants?


By now the delta variant accounts for 50% of all COVID19 cases in countries around the world. The US and UK have witnessed a dramatic rise in cases in the last few weeks too. Owing to this surge, the World Health Organization has declared the Delta variant and its newer mutant as a variant of concern (VOC).

In India, the Delta variant, is called the ‘double mutant variant’ as it has two mutations E484Q and L452R, it originated in Maharashtra last year and spread to the rest of the country. After which, it spread to other countries and is the most prevalent strain worldwide. Epidemiologists in India believe that the Delta variant and its new mutant – Delta Plus have the potential to trigger the third wave. Now, the biggest question on people’s mind is ‘do current vaccines available in India protect against these mutating viruses? And do Indians need a booster dose to improve immunity against such mutants?’


HOW DO VACCINES WORK AGAINST COVID AND ITS MUTANTS?
Post vaccine breakthrough infections are being reported even in fully vaccinated individuals. While non-adherence to COVID-appropriate behavior has a role to play in this, there is no denying the fact that emerging variants of concern have also played their part in reinfections.

The major VOCs in India are the B.1 (the first lineage of ancestral Wuhan virus also called G614), alpha variant, and delta variants. Few cases of Beta and Gamma variants have also been reported in the country. In keeping with this knowledge, scientists from across the world say that the Delta variant can escape the defense shield of vaccines. Yet, inoculation provides enough immunity that can help in avoiding hospitalization. But to understand this better it is important to first understand how these vaccines work.

The vaccines available in the country, Covishield and Covaxin work against the four VOCs. Covaxin (BBV152) is manufactured using the original ancestral variant G614 (virus strain (NIV-2020-770) containing the Asp614Gly mutation). The virus was captured from a COVID patient to ensure that the pathogenetic virus is used for manufacturing vaccine. It was further grown on Vero cell lines and chemically inactivated. Covishield, the ChAdOx1 nCoV-19 vaccine (AZD1222) was developed at Oxford University and consists of a replication-deficient chimpanzee adenoviral vector ChAdOx1, containing the gene for (early) spike protein, nCoV-19. To understand the effectiveness of various vaccines scientists have been working hard to find answers.

In a study conducted by the Public Health England, the Pfizer and AstraZeneca, COVID19 vaccines are effective against symptomatic disease due to the B.1.617.2 variant. Some key highlights of the study are mentioned below:

The two doses of the Pfizer vaccine showed 87.9% efficacy in preventing symptomatic disease due to the B.1.617.2 variant, while the two doses of the AstraZeneca vaccine demonstrated 59.8% efficacy against the B.1.617.2 variant

This study also demonstrated 93.4% efficacy against B.1.1.7 with two doses of Pfizer vaccine vs 66% efficacy with two doses of the AstraZeneca vaccine

But the effectiveness after a single dose of both vaccines was only 33%

WHAT SCIENTIFIC EVIDENCE SAYS: As per the report, a modest reduction in vaccine effectiveness is witnessed. Nevertheless, a clear effect of both vaccines was noted with high levels of effectiveness after two doses. This study also clearly highlights the need to take both doses of the vaccine.

A large study by the Indian Armed Forces (IAF) showed nearly 93% reduction in COVID19 infections amongst IAFs healthcare and frontline workers who had taken Covishield vaccine. The study ‘VIN-WIN’, published on July 27, 2021 in the peer-reviewed Medical Journal Armed Forces India. It also showed reduction in COVID19-related deaths by 98%. This study took place when the country was struggling with the 2nd wave of COVID19. The study revealed that fully vaccinated groups were better off with up to 82% of 1.59 million showing seven deaths only.

Another study by the National Institute of Virology (NIV) examining the efficacy of two doses of BBV152 (Covaxin) against the variants confirmed a reduction in neutralization titers with sera of COVID19 recovered cases (3.3-fold and 4.6-fold) and BBV152 vaccinees (3.0 and 2.7-fold) against B.1.351 & B.1.617.2 respectively. The study highlighted that Covaxin demonstrated a protective response against VOC B.1351 and B.1.617.2. Recently, the NIH has acknowledged the efficacy of Covaxin against the delta variant. But the question is for how long?

HOW WILL WE KNOW WHEN OUR VACCINES ARE LOSING THEIR EFFECTIVENESS? Scientists are searching for biological markers that could reveal when the protection from a vaccine is no longer enough to hold back the Coronavirus. It is possible that a certain level of antibodies marks a threshold: If your blood measures above that level, you are in good shape; but if you are below it, you are at greater risk of infection. Some preliminary studies suggest that these markers — known as correlates of protection — exist for COVID-19 vaccines. Research is underway to find them.

CAN PEOPLE SWITCH VACCINE BRANDS WHEN A BOOSTER DOSE IS AVAILABLE? Yes. Booster doses will take some time to be available in the market. Past experiences and research on other diseases suggests that switching vaccines can strengthen boosters. In the COVID context, the emergence of variants has accelerated research on boosters as well. However, till then building defense through current vaccination programs is a must. If people are waiting for a magical moment to get vaccinated, this is it. It is imperative to note here that both UK (55% fully vaccinated population) with and USA (49% fully vaccinated population), currently in the midst of the 3rd wave of COVID19, have witnessed very few hospitalizations. Which establishes that vaccines offer good protection against severe disease and death. So, while a booster shot may be required in the future, getting both doses of currently available COVID19 vaccine is the cornerstone of protection against COVID19.

Source: https://www.nytimes.com/interactive/2021/world/covid-vaccinations-tracker.html

BUILD YOUR DEFENSE TODAY: It is time that we build our defense and reduce the burden of the pandemic on our health and wellbeing. Remember, the new variants of the Coronavirus are highly transmissible. The Delta variant is around 60% more transmissible than the Alpha variant and causes more severe disease. Aggressive vaccination appears to be the only answer to stop this relentless march of the virus. Any complacency on our part will surely usher in the third wave. Correct and consistent use of masks and adherence to COVID-appropriate behaviour continues to be as important as before for everyone irrespective if people are vaccinated or not.

The article has been authored by
Dr. Rahul Pandit, Director-Critical Care, Fortis Hospitals Mumbai & Member – Maharashtra COVID19 Taskforce ~





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