Booster shots, the way ahead

AMID NATION-WIDE VACCINATION DRIVES, QUESTIONS STILL LOOM OVER EVERYTHING FROM VACCINE EFFICACY TO BOOSTER SHOT REQUIREMENT. AN EXPERT ANSWERS SOME URGENT QUESTIONS

Amid ongoing efforts to vaccinate people, big questions still loom about the vaccine. While some question their efficacy, others wonder about the optimal number of doses, mixing up of vaccines and whether booster shots will be needed.

Several experts claim that it’s too early to speculate about the vaccine or even the duration of its efficacy, given its urgency and newness in the market.

Dr Suneetha Narreddy, MD, ABIM, a senior consultant (infectious diseases) at Apollo Hospitals, answers a list of important questions about the COVID-19 vaccine.

QWILL IMMUNE PROTECTION AGAINST THE CORONAVIRUS BE LONG-LIVED? OR WILL PEOPLE SOON NEED BOOSTER SHOTS?

Currently, it’s not certain how long COVID-19 vaccine protection lasts although studies suggest at least six months. However, vaccine protection wanes over time, as is natural. For some this waning happens more rapidly for reasons such as old age, effects of chronic illness or undertaking treatments that may suppress one’s immune system. Consequently, a booster dose may be needed for people in these high-risk groups to maintain good immune protection.

What are the benefits of booster shots? And when do you think we can start getting booster doses?

Research has shown that booster shots train your body to recognise the virus and defend itself. Human coronavirus epidemics are usually seasonal in nature such as the flu, which typically occurs in the winter months. Hence, booster doses would ideally be before the winter months.

Will the booster be an updated formula?

It’s a possibility. Combining COVID-19 vaccines that generate immunity in different ways — such as Pfizer and AstraZeneca’s — could generate a more powerful and long-lasting immune response. It could also allow for greater flexibility in rolling out a third dose, which might speed things up.

Will we need more boosters in the future?

Possibly yes. This is still a new pandemic, and it’s still not known conclusively how long COVID-19 immunity lasts and how strong it will be. Based on what we know about the original SARS virus, immune responses can last years but may wane. What’s not known is whether these immune responses are sufficient to protect against severe illness or death. If variants continue to emerge, then the vaccines may need to be continually updated.

So will we need a third dose for better protection?

We may require a booster dose in the future, but currently there isn’t much data to suggest benefits of receiving a third dose.

Can different vaccines be mixed and matched?

Mixing vaccine products could be a good idea for many reasons. Supply bottlenecks have led to shortages in several countries, so being able to mix vaccines from different manufacturers may reduce the pressure on vaccine supply. Moreover, there is some preliminary evidence suggesting that it could also potentially lead to a stronger immune response. More data are required to be certain about making it a viable practice.

How will we know when our vaccines are losing their effectiveness?

This is too soon to comprehend. Currently, there are tests to measure the antibodies, which give an idea of the vaccine’s efficacy. We’ll need more tests to understand the half-life and effectiveness of the vaccine.

Would we need a special booster tailored for a particular variant?

Research is ongoing to understand if an immune response to the original version can thwart the mutations or if we require a vaccine targeting a particular variant.

What about all of the people who’ve not received their first dose yet?

People are advised to receive their first dose soon to save themselves from the severity of the disease. The more people get protected the better.

According to a study of 927 people, conducted by Pfizer and published on 1 April 2021, their vaccine offered 91.3% protection against COVID-19, as measured from seven days through to six months after the second dose. According to Dr Sunil Kapoor, Cardiologist, Apollo Hospitals, vaccines generally provide immunity for six months. “If the pandemic persists or if there is a third wave, then a booster dose at six months will be required. Studies are on to understand the longevity of antibodies. Accordingly, recommendations can be made regarding when booster doses are required for a particular vaccine type. Meanwhile, as mutations emerge, vaccines will need to be tweaked accordingly,” adds the doctor.