What happens if you miss your second Covid vaccine dose? WHO answers

The World Health Organization (WHO) answers the most asked questions regarding the Covid-19 vaccine doses.

How far apart should the doses of vaccines be? What if I miss my second dose? Can I get two doses from two different manufacturers? How was safety of vaccines ensured? WHO’s Chief Scientist, Dr Soumya Swaminathan explains in 'Science in 5'.

(Transcript from Vismita Gupta-Smith)

Dr. Soumya Swaminathan: This is an important question. There are so many vaccines now under development and each of them is being given at slightly different dosing schedules.

Most of the vaccines that are being developed need at least two doses, but there are some single dose vaccine candidates as well. The interval between the doses depends on which vaccine you're getting and the local authorities, the government, would have made a guideline and would inform you 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 Astra Zeneca vaccine, where delaying the second dose up to 12 weeks actually gives a better immune boost.

Now, in terms of missing the second dose or being delayed, it's important to get the second dose if the vaccine is a two-dose schedule. 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.

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.

Dr. Soumya Swaminathan: Again, the science is changing and evolving and the knowledge base is growing.

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 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.

This post originally appeared on https://emongsjournals.blogspot.com