Vaccines more than 90% effective: towards the end of the Covid-19 epidemic?

A researcher prepares samples during the research and development of a vaccine against the coronavirus at a laboratory at the biotechnology company Biocad in St. Petersburg (illustrative image).

REUTERS / Anton Vaganov

Text by: Simon Rozé Follow

6 min

The Pfizer laboratory announced Monday, November 9: its candidate vaccine against the coronavirus is 90% effective.

Wednesday 11, Russia outbid: 92% efficiency for his, Sputnik-V.

With such levels of efficiency, can we foresee the end of the pandemic?

It is still far too early to tell.

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These

vaccine efficacy

are good news that we have not had for a long time on the front lines of the fight against Covid-19.

However, they should be greeted with hindsight, because many questions still have no answer.

Indeed, the bad habit taken since the beginning of the pandemic is perpetuated, the laboratories announce their results by press releases rather than by studies published in scientific journals, even if Russia is committed to do so in the next days.

Sharing data from these clinical trials would, however, be very useful: for example, we do not know whether this announced efficacy concerns everyone, including people at risk.

This information is however capital.

It should also be remembered that these announced results are only preliminary.

For Pfizer, for example, the advertised efficacy was measured just 28 days after the administration of the first dose of its vaccine candidate.

We therefore do not know if it remains at this level any longer: only time will be able to tell.

Yet despite these unknowns, Pfizer plans to distribute the first doses by the end of the year.

The European Union also announced on Wednesday that vaccinations would be possible in the first quarter of 2021. These reservations only concern efficiency, and 90% is a much better result than expected.

For vaccines developed so quickly, scientists would have been satisfied with 50%.

Therefore, even if this effectiveness were to decrease as the clinical trials progress and the analysis of their data, these vaccines will have their role to play in the fight against the epidemic.

A widespread vaccine?

The latter could be major in controlling the pandemic, but it will not however solve all the problems and the Covid-19 will not disappear because vaccines will be available;

at least not immediately.

There are indeed several challenges to overcome: the first of them being immunization coverage.

For a vaccine to be effective, a very large majority of the population must use it, so that there is no chance for the virus to continue to spread.

Unfortunately, at the present time, mistrust undermines this objective.

A study published in

last October, conducted in 19 countries, revealed that on average a quarter of their population was not ready to be vaccinated: “ 

 ”explains Jeffrey Lazarus, who led this study for the Institute of World Health in Barcelona.

“ 

 "

This pitfall is not the only one to overcome.

There are also serious logistical questions about making these vaccines available to everyone.

For example, Pfizer's vaccine should be stored at -80 degrees.

Under these conditions, very many communities, especially rural ones, will simply not have access to it.

It will therefore be necessary that other types of vaccines are also available, otherwise the virus will continue to circulate in certain regions of the world and the goal of the end of the pandemic can never be truly achieved.

What about mutations in the virus?

Finally, the effectiveness of a vaccine over time also depends on the coronavirus itself.

Mutations could have an effect.

The Sars-CoV-2 responsible for Covid-19 uses a key to enter our cells and infect them, what is called the S protein. To fight it, we can therefore try to neutralize this S protein. The virus cannot then no longer enter our cells to multiply there: this is what our immune system does and it is the basis of most vaccine strategies.

But what happens if this S protein changes as the virus naturally mutates?

A team of researchers in 12 countries studied a variant of the coronavirus, the second most

.

This work has not yet been published, so we must understand them with the usual reservations, but they observed that this strain had a difference in its protein S, making our immune response less effective.

Consequently, while mass vaccination would act well on the dominant strain, it would on the other hand have less effect against this variant.

The latter would therefore have free rein to spread and could become the majority over time.

For all these reasons, a vaccine will never be the only answer in this crisis.

It will only be a tool, very good certainly, but to be used in combination with the respect of barrier gestures, screening of patients and identification of contact cases ... Faced with a pandemic, there is no solution miracle.

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