Virologists warn against skipping second dose of Covid-19 vaccine

PUNE: Leading virologists have stressed on the need for strict adherence to the two-dose regimen of the Covid-19 vaccination, saying that while the first dose acts as a launchpad and primes the immune response, the second amplifies and makes the immune response against the virus stronger.
Against the looming concern that some of the beneficiaries in the priority groups might not turn up for the second dose of the vaccine after taking the first shot, virologists urged them not to deviate from the norm as the second dose adds to the durability of protection.

The first dose initiates an immunological response against the antigen introduced in the body through the vaccine. The body develops IgG and neutralising antibodies (protection) within three to four weeks of taking the first shot.
“The second dose ensures that it boosts not only the virus-specific antibodies but also the T cells (T-lymphocytes) — the killer cells which are part of the broader immune response against the virus. It (second dose) also adds to the durability of protection,” said senior scientist Raman Gangakhedkar, former head of the epidemiology and communicable diseases’ division of the Indian Council of Medical Research (ICMR).
The experts also warned against lowering the guard during the period of vaccination — right from the first shot to even days after taking the second dose — as the nationwide Covid vaccination of healthcare workers begins on Saturday. Sticking to Covid-appropriate behaviour such as wearing masks and maintaining social distance continues to be key in the fight against Covid-19 even after full vaccination.
“It is important to adhere to the evidence generated by the manufacturer through the vaccine trials and take two doses. Single-dose and the duration for which it will protect currently lacks in data,” said Gangakhedkar, who joined the prestigious Dr C G Pandit National chair at the ICMR this year.
Vaccine researcher Prasad Kulkarni, the lead investigator of one of the two Covid vaccines rolled out for the vaccination of priority groups in India, said, “The body develops protective antibodies (IgG and neutralising) by the four weeks after the first shot. The second shot taken at this crucial point pushes the level of the virus-specific antibodies exponentially. The first dose will certainly provide him/her protection against the virus for some time, but how long it will last is questionable.”
He said, “The first dose creates a sort of launchpad on which the body’s immunity against the virus takes off, with the second dose increasing the antibodies multiple times, which give long-lasting immunity against the virus.”
In layman’s terms, if the first shot develops 100 virus-specific antibodies in the blood, the second shot simply helps shoot up this level to 700 antibodies within the next four weeks.
“That simply means a vaccinee is fully protected against the virus within two months. However, it is certainly advisable that they continue to use masks, wash hands frequently and maintain social distance even after full vaccination,” Kulkarni said.
Senior virologist Deepak Gadkari, former director of the National Institute of Virology (NIV), said, “Vaccine trials and laboratory studies have also noticed a boosting effect with the second dose of Covid vaccine. It is prudent to go for the second dose of vaccine to get better and longer protection against the disease.”