Saturday, 18 September, 2021

Covid: Vaccinated will it be necessary to be re-vaccinated?

  • Sun Online Desk
  • 3rd August, 2021 08:18:42 PM
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The increasing prevalence of new variants of the coronavirus raises more and more questions about the level of protection even after vaccination.

The microbiologist and specialist in infectious diseases William Petri , of the University of Virginia, answers the most frequent questions about vaccines and their recall in 6 points.

What is a vaccine booster?

A vaccine booster is the injection of an additional dose, intended to maintain immune protection against a given pathogen. The process is common because our immunity can weaken over time quite naturally. For example, the flu shot must be repeated every year, those against diphtheria and tetanus every ten years.

In Israel , the authorities are encouraging people over 60 to take a third dose.

Long-term immunity is also provided by plasmoblasts. These cells, other actors in the production of antibodies, do not need a booster and were detected eleven months after injection in vaccinated people: which suggests the establishment of an effective immune memory.

How do I know if a recall will become necessary?

A sign of the need for a booster would be the growing epidemic among those vaccinated.

In support of this idea, a study showing that mRNA vaccines (Pfizer and Moderna), which appear to be the most effective, generate a higher level of antibodies in the blood than adenovirus vaccines (Johnson & Johnson and AstraZeneca ).

A preliminary study also suggests that the level of anti-Spike antibodies would be lower in former Covid-19 patients, including after injection of the AstraZeneca vaccine.

But until researchers know for sure how to measure immunity induced by vaccination, the sign to follow as to the need for a booster will be.

(Times of India)