True or false: Countering the claims of Covid-19 vaccine sceptics

Anti-vaxxers say Covid-19 vaccines are at best ineffective and at worst dangerous. FRANCE 24 spoke to an epidemiologist who responded to these claims.
Anti-vaxxers say Covid-19 vaccines are at best ineffective and at worst dangerous. FRANCE 24 spoke to an epidemiologist who responded to these claims. © Sam Yeh, AFP

“Vaccinated people die of Covid-19”, “messenger RNA modifies our genetic code”, “you can transmit the virus even if you’re vaccinated” ... Anti-vaxxers’ arguments against the Covid-19 shot keep spreading, while the vaccination pace in France slows down. But do these arguments hold water? FRANCE 24 spoke to Antoine Flahault, an epidemiologist, who countered some of the most common claims.


More than six months after the start of the vaccination campaign in France, Covid-19 vaccines are still causing a stir. Anti-vaxxers continue to insist that jabs are at best ineffective and at worst, dangerous. With some scientists in France also saying they are anti-vaccine, many French people no longer know which way to turn.

And yet, Health Minister Olivier Véran has warned that with the highly contagious Delta variant spreading fast, a vaccination slowdown threatens to bring about a fourth wave of the coronavirus in France at the end of July.

On social media, arguments against the vaccines abound: “They’re ineffective against the Delta variant”, “messenger RNA vaccines cause cancer”, or “the side effects are worse than Covid-19 itself”.

Professor Antoine Flahault, an epidemiologist and director of the Institute for Global Health at the Faculty of Medicine of the University of Geneva, said that though ardent vaccine opponents are unlikely to change their minds, many people have real concerns about the vaccines.

“Anti-vaxxers represent only a very small proportion of the French population, less than about 3.5 percent,” said Flahault. “Nothing will change these people’s minds. But anti-vaxxers aside, there’s a much larger number of people who ask themselves very legitimate questions, which I will try to answer.”

  • True or false: ‘Covid-19 vaccines were developed too quickly, so can’t be trusted’

Yes, it’s true that they were developed very quickly, and it’s also true that these are new, innovative vaccines, especially the RNA messenger vaccines. That said, what was compressed to save time were the administrative phases of carrying out clinical trials, not the phases dealing with ethics. The ethics committees were consulted as always and gave their opinions and responses as usual. It was the pandemic that made it possible to accelerate the recruitment of subjects.

A vaccine is currently being developed for the Ebola virus, but there were never many opportunities to recruit patients. To recruit 30,000 people, and to observe a difference between the placebo group and the vaccine group, there needs to be a significant epidemic: If the virus isn’t circulating, or only a little, that becomes very difficult.

I remember conducting a clinical trial with chloroquine for the chikungunya virus, because it was thought to have an effect, but we had to stop for lack of subjects.

The conditions that contributed to the rapid development of the Covid-19 vaccine are linked to the epidemiology.

  • True or false: ‘Some vaccinated people also test positive or are hospitalised, which proves that the vaccine is ineffective, especially against the Delta variant’

You just need to look at what’s happening in Israel or the UK, where they are currently experiencing a wave connected to the Delta variant. When we observe the correlation between contamination cases and hospitalisations, intensive care and mortality, there is, in fact, an absence for the moment of mortality associated with the variant.

At the same time, in Russia, where much less of the population is vaccinated (around 15 percent have received the first dose, compared to more than 65 percent in the UK), there is a significant wave of mortality, with nearly 800 deaths a day, and also a real wave in South Africa, where we’ve seen an increase in the number of positive cases and deaths.

In Portugal, which is nearer to other European countries in terms of vaccinations (more than 50 percent), there has perhaps been a small increase in hospitalisations, but it seems to be much smaller – in any case not on the same scale as in Russia.

So here we have a practically live demonstration of how the vaccine, above a certain threshold, begins to work. But this does not mean there won’t be any more hospitalisations: In the UK, a fraction of the people are not yet vaccinated, and it is precisely those people who are being hospitalised, not those who are vaccinated.

Either way, of course there can be glitches and a few vaccinated people might still contract the virus. There are even some who might experience serious complications and die. But there is always marginal vaccine ineffectiveness; it’s very low for Covid-19 vaccines, but a vaccine is never 100 percent effective. Covid-19 vaccines are very close to 100 percent.

Apart from very rare cases linked, for example, to immunosenescence, where very old people may lose their immunity to a vaccine, when you are vaccinated, you are no longer at risk of needing hospitalisation. We are really dealing with very effective vaccines.

  • True or false: ‘You can still transmit the virus even if you are vaccinated’

The vaccine reduces the risk of transmission, probably by 60 to 80 percent. It isn’t 100 percent, but in terms of public health, very substantially reducing the risk of transmission helps reduce the risk of the virus spreading. So the more people are vaccinated, the more we will be able to block this virus, and the more difficult it will be for it to spread through the population.

However, this cannot be done fully: Very few vaccines entirely eliminate the risk of transmitting the virus. Covid-19 vaccines may allow some transmission, but they protect us against the severe forms, and that’s what we we need them to do.

  • True or false: ‘Messenger RNA vaccines modify our genetic code’

This is a claim we hear a lot. When you have Covid-19, a huge strand of RNA enters the cells, takes on the role of messenger RNA and produces proteins from our cellular machinery.

When you’re infected by a virus, whether it is influenza, dengue, chikungunya or Covid-19, it’s an injection of messenger RNA. And when it’s caused by a mosquito, it’s very similar to a messenger RNA vaccination. So there is nothing very new here, but above all, there is no genome modification with these viruses. The only genome modification that exists is with retroviruses, like the AIDS virus, which can get into the genome, but this is not at all the case with messenger RNA viruses.

I can't understand how you can be afraid that a vaccine will do something worse than the virus you’re trying to fight. Especially since the vaccine’s messenger RNA is destroyed within hours, to the point that a second dose is necessary. Messenger RNA has no subsistence in cells beyond a few hours.

  • True or false: ‘Messenger RNA vaccines like Pfizer can cause cancer’

This claim is hard to counter because cancer, which can be caused by carcinogens, doesn’t appear in the weeks or months following exposure, but years later. So these would be cases of cancer that would appear later and we’d then have a cancer epidemic in several years.

You just can’t counter this claim. If a former Nobel Prize laureate says ‘There will be a cancer epidemic in 30 years’, how can I say he’s wrong? I can’t know. [Editor’s note: this is a reference to Professor Luc Montagnier, today criticised by an overwhelming majority of scientists for his anti-vaccine positions.]

On the other hand, what we can say is that with everything we inhale, swallow and inject, we might be at risk of exposure to carcinogens. We know, for example, that the fine particles that we breathe in the atmosphere on peak pollution days are carcinogenic. Maybe we’ll develop cancer from the air we breathed last winter, when pollution in our cities peaked. I think there’s no model that has ever shown that this vaccine causes cancer, so there is no reason to think that it does.

  • True or false: ‘The vaccine’s side effects are more dangerous than the disease’

As an individual, if you’re young and you get severe cavernous sinus thrombosis, which is a very serious side effect, or myocarditis, an inflammation of the heart muscle, for which you’re often hospitalised, then yes, in that case, your side effect is more serious than what the Covid-19 might have done to you, if you're young and without other risk factors. However, this is extremely rare – so rare that health agencies believe that the benefit far outweighs the risk.

We saw this with smallpox. The vaccine was sometimes very dangerous since it could kill one person per every millions of people vaccinated. But when smallpox was rampant and killing two million people a year worldwide, no one questioned the value of the smallpox vaccine. Once the risk disappeared, after smallpox was eradicated, we stopped vaccinating because of the adverse effects.

Likewise, the Covid-19 vaccine can sometimes cause serious effects, even if not death. To manage this, we can only say under what circumstances (such as age, or sex) the side effects occur and this allows us to regulate the prescription of some of these vaccines, not all of which carry the same risk of serious side effects.

Any medical product can potentially cause serious side effects. Unfortunately, that’s the downside of any effective medicine.

  • True or false: ‘If you have a healthy lifestyle, your immune system can defend itself on its own and doesn’t need a vaccine’

If there was a healthy lifestyle that allowed you to fight against such aggressive viruses, we would have known, we would have experienced or observed it. I, personally, haven’t seen it.

Being in good health allows you to resist the attacks of the virus longer and more strongly: If you end up in intensive care, it’s better not to be too thin or in poor health. But that, unfortunately, is all that can be achieved by having led a healthy lifestyle before contracting the virus.

Of course, if you believe a healthy lifestyle means not being in close contact with anybody, that might be a way to protect yourself – not ever being in a situation where you might contract the virus. But other than this plan, which is quite rare and extreme, the immune system cannot be sufficiently boosted to be able to spontaneously resist the virus.

This article was translated from the original in French.

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