Amid worry, here's what the world's most prominent scientists say about the COVID-19 vaccine


Published: 2020-12-12 16:14

Last Updated: 2023-03-27 02:01

Photo: USA Today
Photo: USA Today


The first vaccines against COVID-19 have arrived, and ordinary people have concerns about their potentially harmful effects. Here's what we know about it for now.

What are the side effects?

Detailed data was published this week and the two of the most advanced vaccines are considered safe.

Trial data on the Pfizer/BioNTech vaccine, which has been licensed in several countries, was published in the New England Journal of Medicine after it was revealed by the US Medicines Agency.

The clinical trial, which included about 40,000 volunteers, showed that this vaccine causes classic side effects, often painful but without risk to patients: 80 percent of those who received the vaccine felt pain around the injection site, and many of them felt fatigue, headache and stiffness. Some also experienced temporary swelling of the nodes. These side effects were more frequent and severe in younger adults.

Data for the vaccine, which AstraZeneca is developing with the University of Oxford, UK, has been published in the prestigious medical journal The Lancet. The results indicated that this vaccine is "safe," according to the Lancet, after a clinical trial that included 23,000 volunteers.

The two vaccines are based on two different technologies. Pfizer/BioNTech used a pioneering technology known as messenger RNA, and the AstraZeneca Oxford vaccine relied on a "viral vector" it carried, which is a harmless virus (adenovirus from chimpanzee).

- High level?

In France, an uproar was raised after statements made by an infectious disease specialist Professor Eric Kum, who confirmed through several media that he was reluctant to receive the Pfizer/BioNTech vaccine, especially since he had “never seen” a recurrence of side effects in this “very high” way.

But his statements were greeted as lukewarm by many other scholars. Virologist and vaccination specialist Mary Paul Kenny objected to saying that one vaccine was preferred over another, likening that to someone saying that he "prefers chocolate ice cream instead of strawberry ice cream."

"We know that these vaccines induce strong reactions: their safety level is completely satisfactory, but on the other hand, they cause pain in the arm and a feeling of fatigue. This should be clear to the citizens," she said Friday during a parliamentary hearing.

"I compared these effects with the effects of 'children's vaccines' that can tire the child because they are annoying, perhaps for a day, but this reaction lasts for a short time, so if it is combined with high levels of protection, I think it should be acceptable."

Immunologist Alain Fischer, who is being used by the French government to guide its vaccination strategy, affirmed that these effects "cannot be considered (...) serious harmful effects."

How many serious side effects are there?

In the case of the Pfizer/BioNTech and AstraZeneca/Oxford vaccines, side effects are still rare at this stage. Only one patient receiving the AstraZeneca/Oxford vaccine experienced "serious side effects related" to the injection, according to data published in The Lancet. He developed transverse myelitis (a rare neurological disease) that temporarily halted the trial in early September.

Two other cases of serious side effects were detected, without being attributed to the vaccine.

"The three participants have either recovered or are on the way to recovery," said those responsible for the experiment.

In the case of the Pfizer/BioNTech vaccine, the only potentially worrisome side effect was four cases of Bell's palsy, which is often temporary paralysis.

But its frequency (4 cases out of 18,000 people who were followed for two months) does not differ from the general percentage recorded for this paralysis, and therefore it is not known whether it was the vaccine that caused it. As a precaution, the US Food and Drug Administration recommended increased monitoring.

Finally, there were eight cases of appendicitis in the vaccinated subjects, compared to four in the placebo group that received a neutral product in order to be able to make a comparison. But the US Food and Drug Administration thinks it's just a statistical fluke, and it has nothing to do with the vaccine.

As with any drug, the hypothesis that these vaccines have serious side effects cannot be ruled out. But in medicine, a substance is evaluated by looking at the balance between its benefits and risks.

Isabel Baran, a vaccine expert at the French Medicines Agency, said Friday that "given the benefits of the vaccine and its effectiveness for people exposed to severe symptoms of Covid, (...) it is completely acceptable to have a vaccine that reacts strongly to the body if its harmful effects are not serious."

What about sensitivity?

The day after the start of the Pfizer/BioNTech vaccination campaign in the UK Tuesday, British authorities announced that two people had responded poorly to the vaccine. Both of them became so sensitive that they needed adrenaline.

This has resulted in health authorities recommending that this vaccine not be given to people who have in the past suffered a "significant allergic reaction to vaccines, drugs, or foods (such as anaphylactic shock) or those who have been advised to carry an adrenaline injector."

However, Professor Stephen Evans, professor of pharmacological epidemiology at the London School of Hygiene and Tropical Medicine, as quoted by the British Science Media Center, said, "This does not mean that the general public should be concerned about receiving this vaccine."

Moreover, those responsible for the clinical trial that led to the license granted to the Pfizer/BioNTech Alliance in several countries anticipated such risks: they excluded volunteers with a history of severe allergies to vaccines in general or to one of the components of the vaccine.

But this does not seem to be of concern to the millions of people who are allergic to eggs or peanuts, for example.

An expert from the University of Oxford, Professor Graham Ugg, as quoted by the Science Media Center, noted that it is "important to understand accurately the reactions" caused by the vaccine to the British "and to know their medical history, to better understand the risks."

What are the pending issues?

The main issue is the hypothesis of unwanted effects that may occur later, as we know very little about these new vaccines.

Even if it is authorized in a hurry due to the pandemic, global health authorities will continue to check their data as vaccinations progress so that they can respond immediately if necessary.

This monitoring is called pharmacovigilance when it comes to drugs and vigilance about vaccinations when it comes to vaccines.

"This monitoring will help us monitor any potential signs of side effects," the Science Media Center quoted Doctor Charlie Wheeler, a vaccination officer at the charity Wellcome, as saying.

The French Medicines Agency said Friday that a report will be published every week on the adverse reactions reported.