Vaccinated but contagious? This is the idea that goes against what one expects from vaccine, but it remains a serious topic. Although the Haute Autorité de Santé has no doubt as to the effectiveness of the upcoming Covid-19 vaccine, it yet expresses a doubt as to its ability to fully stop the spread.
In a release – published online on November 30, 2020 – the public authority takes the contagion risk very seriously and would rather wait for “studies to prove that vaccines are effective on the virus spread” before approving the launch of the vaccine campaign.
Vaccines studied today – and expected to be issued within a matter of weeks – have been first and foremost developed to avoid serious complications of coronavirus; but they have no impact on the spread of the virus. Vice president of the vaccination technique committee professor Daniel Floret tells Le Parisien that “vaccine stops the disease at the level of the lungs, but does not prevent the virus from entering the body, and this is the problem. For it to prevent from spreading, it shall prevent the virus from entering airways”.
It is then possible that someone vaccinated shows some minor symptoms and spreads the virus. Other experts, interviewed by Le Parisien, disagree on the degree of effectiveness of the upcoming vaccine as to the spread of the virus. CNRS research director Bruno Pitard thinks the real risk is here: “to give you a picture, if you have 100 viral particles and it stops 80 of them, there are still 20, you can have a few symptoms. If you go to the movies and cough next to someone without a mask, you might contaminate them”.
Jean-Michel Pawlotsky measures this idea. According to the virologist at the Henri-Mondor university hospital in Créteil, “its theoretically possible, vaccine is no Darth Vader armor” he warns, “but as a matter of fact, it is quite unlikely”. “At first, it is possible the virus infects cells a bit before antibodies block them, but the immune response is very quick” he adds.
According to Pawlotsky, there is no reason the virus acts differently from the others: with this novel immunity, the body is said to know how to recognize and fight the virus quickly as it could be trying to enter organism. The virologist insists on the importance of a large-scale vaccine campaign: “what matter is the collective dimension. The number of people immune will be so big that the risks of spreading Covid will grow weaker over time, and to do so, we need mass vaccination”.
But there are people caught in between. Immunologist Jacqueline Marvel is for the precautionary principle as proven by the Haute Autorité de Santé. According to the scientist, even though vaccinated, people shall not let go of health guidelines and facemask-wearing. Marvel thinks that vaccine will work as expected: “to my knowledge, vaccines stop the spread”.
She say, herd immunity by vaccinating as many people as possible will enable to dramatically curb the spread of Covid-19. This mass vaccination will yet have to take place over months: prioritized people are expected to be the first ones to get the first wave of vaccine in early 2021.
