Second jab critical
Receiving the second dose of the COVID-19 vaccination is important if the vaccine is a two-dose schedule.
Dr. Soumya Swaminathan said that it doesn’t matter if it’s early by a few days, or late by a few days, or even a couple of weeks.
“It’s important to go back and get that second dose because the first dose actually presents this new antigen to the immune system to prime it,” the World Health Organisation (WHO) Chief Scientist explained.
“And the second dose is the one that really gives a boost to the immune system so that the antibody response, as well as T cell mediated response, they are very strong and they also develop a memory response, which then lasts for a long time, so that when the body sees this antigen again, this virus protein again, it knows that it needs to react quickly.”
She said that the interval between the doses depends on which vaccine is being administered, also pointing out that the local authorities – the Government – would provide guidelines and inform recipients about when the second dose is due.
“Most of the two-dose vaccines currently are being given between three to four weeks between the first and the second dose. But there is some data from some vaccines like the AstraZeneca vaccine, where delaying the second dose up to 12 weeks actually gives a better immune boost.”
As it relates to having your two doses from two different manufacturers, Dr. Swaminathan said that the science is changing and evolving, and the knowledge base is growing.
She went on to reveal that there are now clinical trials ongoing in some countries that are looking at interchangeability, “which means the first dose with one vaccine and the second dose with a different vaccine, maybe even a different platform vaccine. And immunologically, there are reasons why this would make sense. However, at the present time, there isn’t enough data for us to recommend this type of interchangeable two-dose schedules”.
“And so, for the time being, the policy advice that WHO has put out, which is the Strategic Advisory Group of Experts (SAGE) guidelines on how to use vaccines, we’ve done it for the Pfizer vaccine, the Moderna vaccine, the AstraZeneca vaccine, and currently SAGE is reviewing the data from the other vaccines that are in the pipeline. And so, we need to follow what’s in that policy advice and for the time being, it is recommended to have the second dose with the same vaccine as you had the first dose,” she advised. (TL)