Pfizer-BioNTech’s mRNA Covid-19 vaccine became the first in the US early this month to receive emergency approval to be administered as a booster shot or third dose.
US President Joe Biden got a third Pfizer dose in line with the approved health guidance, which allows boosters for those 65 years or older. But the clamour for a third dose is seeing some traction. Countries including the UK, France, Germany, and Israel have introduced booster shots on a conditional basis.
Experts told Moneycontrol that only those who are immunocompromised may need a booster shot.
Who needs a booster shot?
To be sure, all people don’t need a booster or third dose at the moment. Even in the US, the emergency approval of the third dose is limited to people over 65, nursing home residents who received the Pfizer vaccine, and the younger population whose occupation puts them at high risk of getting infected with Covid-19.
Frequently Asked Questions
A vaccine works by mimicking a natural infection. A vaccine not only induces immune response to protect people from any future COVID-19 infection, but also helps quickly build herd immunity to put an end to the pandemic. Herd immunity occurs when a sufficient percentage of a population becomes immune to a disease, making the spread of disease from person to person unlikely. The good news is that SARS-CoV-2 virus has been fairly stable, which increases the viability of a vaccine.
There are broadly four types of vaccine — one, a vaccine based on the whole virus (this could be either inactivated, or an attenuated [weakened] virus vaccine); two, a non-replicating viral vector vaccine that uses a benign virus as vector that carries the antigen of SARS-CoV; three, nucleic-acid vaccines that have genetic material like DNA and RNA of antigens like spike protein given to a person, helping human cells decode genetic material and produce the vaccine; and four, protein subunit vaccine wherein the recombinant proteins of SARS-COV-2 along with an adjuvant (booster) is given as a vaccine.
Vaccine development is a long, complex process. Unlike drugs that are given to people with a diseased, vaccines are given to healthy people and also vulnerable sections such as children, pregnant women and the elderly. So rigorous tests are compulsory. History says that the fastest time it took to develop a vaccine is five years, but it usually takes double or sometimes triple that time.
Why do certain people need boosters?
Dr Rahul Pandit, director of critical care at Fortis Hospital - Mumbai and a member of Maharashtra’s Covid Task Force, said that at the moment, scientific evidence supporting the use of a booster or third dose is limited.
“While antibodies wane over time, the T-cell memory responses that offer long-term protection are expected to remain,” Pandit said.
He said the antibody response generated by vaccines typically lasts 9-12 months.
“But in certain populations like the elderly, healthcare workers and frontline workers, people taking medications that suppress their immune system, and those with compromised immune systems due to other disease conditions may be at risk of getting infected post-vaccination,” Pandit said.
Data suggests that the Pfizer vaccine’s protection wanes over the six months following vaccination. Similar data isn’t there for other vaccines. India widely uses Covishield (identical to the AstraZeneca vaccine) and Covaxin. Covishield is based on a viral vector platform and Covaxin is based on an inactivated platform.
What is India's position on booster doses?
The Central government has said booster doses are not a priority at the moment and the top focus is on getting people fully vaccinated with two doses.
“This makes sense when a lot of people haven’t even got their first dose,” said Pandit.
Dr Gagandeep Kang, vaccine expert, and professor of microbiology at the Christian Medical College in Vellore said the government should consider boosters for the immunocompromised. In the future, boosters should be considered for other vaccines, based on their respective platforms, Kang told Moneycontrol.
The government may have also looked at data on severe breakthrough infections of those who end up in hospitals and the virus variants that cause them to get an idea of which population groups are at high risk before it proceeds to allow booster doses.
India has administered 876.6 million doses of Covid-19 vaccines, with almost 20 percent of the people fully vaccinated.
What are the challenges for the booster dose?
Booster doses may further aggravate the supply-demand mismatch of vaccines globally. Public health groups have said booster doses may foster wider inequity in the distribution of vaccines as rich countries and those with vaccine manufacturing capabilities will corner supplies.
According to the latest supply forecast by COVAX, a multilateral initiative aimed at guaranteeing global access to Covid-19 vaccines, a 25 percent reduction is expected in anticipated supplies for 2021. COVAX expects about 1.4 billion doses to be available in 2021.