1-yr vax dose gap fine but 4 weeks ideal: Top virologist

1-yr vax dose gap fine but 4 weeks ideal: Top virologist

Advisory Leaves Senior Citizens Confused

Sunitha.Rao@timesgroup.com

Bengaluru:15.05.2021

The Centre’s advisory to states to extend the interval between the first and second doses of Covishield vaccine to 12-16 weeks from the earlier 6-8 weeks has left many senior citizens confused. Those who took the second dose after six weeks are now concerned about the efficacy of the vaccine and whether it would offer protection from severe infection.

“We took the second dose within the 6-8 weeks window but the latest advisory suggesting an interval of 12-16 weeks has left us confused,” said Sridhar MS, 61, from Malleswaram, Bengaluru. A retired banker, Sridhar, had travelled all the way to Bidadi PHC, about 35km away, with his mother and wife on Wednesday to get the second shot.

However, experts TOI spoke with said delaying the second dose was fine from a medical point of view, especially given the shortage of doses. They pointed out that protection against the virus heavily depends on an individual’s immune response capabilities.

Dr T Jacob John, retired professor and head of clinical virology and microbiology at Christian Medical College, Vellore, said there is absolutely no problem if the second dose of Covishield is delayed. He said it is as good as taking after four weeks.

“The protection it offers after a four-week interval is nearly 100% against a severe form of the disease,” Dr John explained. “But it is not 100% against mild and moderate Covid. If you increase the interval up to 12 weeks, the efficacy against mild to moderate disease increases. However, against severe disease, the efficacy is the same whether the interval is four weeks or 16 weeks.”

He said a delayed second dose is as good as an early second dose and it does not nullify the effect of the first dose, which remains the same up to one year.

Dr Chandrashekar S, popular rheumatologist and immunologist, concurred. “There is always confusion between science and policy making,” Dr Chandrashekar said. “Conceptually, when the Covishield vaccine was studied, the two doses were spaced out by four weeks. The effectiveness was a little superior when the two doses were taken 12 weeks apart, as per the study,” said Dr Chandrashekar. Those who are concerned about immunization benefits can take an antibody test, he added.

However, Dr John conceded no study has been conducted to test efficacy beyond a 12-week window. “We are using the science of vaccinology to predict efficacy,” he said.

Full report on www.toi.in

A SHIELD: Beneficiaries above 18 years receive the Covid-19 vaccine in Patna on Friday