Covid-19: Faced with the lack of vaccines, is one dose enough instead of two?

The effectiveness of the vaccine is not guaranteed if only one dose is used instead of the two recommended.

REUTERS - DADO RUVIC

Text by: Simon Rozé Follow

5 mins

About thirty countries have started their vaccination campaigns against Covid-19 and already there are stock problems.

To remedy this, a solution has been put forward, in particular on the side of the United Kingdom: use only one dose instead of the two recommended.

However, the effectiveness of this protocol is not guaranteed.

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The Pfizer / BioNTech vaccine requires two doses to be injected 21 days apart.

The British, however, plan to distribute all their available doses to vaccinate as many people as possible.

They would then make their recall several months later.

Unfortunately, if this strategy makes it possible to go faster, it is not without consequences on the quality of the immunity conferred by the vaccine.

The first dose induces an immune response, the second increases it and allows it to last over time 

", explains Jean-Daniel Lelièvre, head of the clinical immunology and infectious diseases department at the AP-HP Henri-Mondor hospital. .

“ 

For questions of immunology and optimal maturation of the cells that produce the antibodies, two injections must be given in three weeks.

It is not to the day, but we do not know what would happen if instead of three weeks, we went to three months, 

”he continues.

For lack of knowledge, it is therefore impossible to say whether such a vaccination schedule would be effective or not.

BioNTech, which developed the vaccine produced by Pfizer, also publicly recalled this Tuesday, January 5.

Can we use two different vaccines?

For the same reason, the UK plans to authorize the administration of a second dose from a vaccine other than the one used for the first.

This will only be exceptional, in case for some reason the first vaccine is no longer available.

This concerns those of Pfizer and Moderna "

 There is possibly an interchangeability between these vaccines 

", explains Jean-Daniel Lelièvre.

 They use the same

 : Cost of delayed vaccination: '2 billion euros per week lost, maybe more'

technology.

It is in any case more likely than between two very different vaccines like those of Pfizer or Moderna on one side and that of Astra Zeneca on the other 

”.

These vaccines do not provide the same training “target” for the immune system.

Authorization of Moderna vaccine in Europe

The

vaccine Moderna

was also approved Wednesday, January 6 by the European Medicines Agency and the European Commission immediately issued him a conditional authorization for the market.

It is thus the second vaccine to be authorized in the European Union after that of Pfizer / BioNTech.

New doses will therefore be available, which will relieve the pressure on stocks in several countries.

The data from the clinical trial of this vaccine have also finally been published in a scientific journal, the

New England Journal of Medicine.

 The article is open access, and all data is there transparently.

Also listen: Cost of delayed vaccination: "2 billion euros per week lost, maybe more"

Still no treatment

Vaccination is to prevent disease, but its curative counterpart unfortunately does not have the same success.

A new hope has indeed been disappointed: that of monoclonal antibodies.

This involves using antibodies from people who have recovered from Covid-19 to administer them to those who are fighting the disease.

A Phase 2 clinical trial revealed encouraging data.

Phase 3, however, did not confirm the hope.

We thus read, once again in the

New England Journal of Medicine

, that it was discontinued for " 

futility

 ", that is to say that no efficacy was observed.

Almost a year after the global spread of the disease, there is therefore still no effective treatment against Covid-19.

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