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Covid-19: What is known about the first side effects of vaccines

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Fatigue, allergic reactions, muscle aches. In a report published on December 8, scientists from the Food and Drug Administration (FDA) detail the first adverse effects of the Covid-19 vaccine manufactured by the laboratories Pfizer and BioNTech. Find out what are the side effects of this Covid vaccine.


Like any medicine, a vaccine can cause side effects. A few hours after vaccination, pain, redness, or swelling may occur at the injection site. This frequent and harmless reaction goes away after hours or days. This type of side effect can appear after a vaccine against hepatitis B, against pertussis but also against Covid-19.

A first analysis of the Pfizer-BioNTech vaccine, published by the Food and Drug Administration (FDA) on December 8, reveals that this local reaction is one of the first adverse effects of the anti-Covid vaccine. However, this is not the only side effect caused by this vaccine.

What are the first side effects of the Covid-19 vaccine?

In its report, the US Drug Agency lists the side effects of the Covid-19 vaccine manufactured by the laboratories Pfizer and BioNTech. To do this, it was based on the results of the clinical trial of the vaccine. The trial in question began last July and was held in several countries with 44,000 people. Half of the participants received the Covid vaccine and the other half received a placebo.

According to the Food and Drug Administration, the main side effects of the Covid-19 vaccine are injection site reactions (84.1%), fatigue (62.9%), headaches (55.1%) , muscle aches (38.3%), chills (31.9%), joint pain (23.6%) and fever (14.2%). These different local or systemic reactions are classic side effects that can occur after any vaccine.

According to the analysis, reactions were more frequent after the second dose of the vaccine. Side effects were generally less common in adults compared to younger participants.

Another side effect: Bells palsy. This facial paralysis, which is characterized by the partial or total loss of function of certain facial muscles, was reported by four participants who received the anti-Covid vaccine. "From the first dose to a month after the second, there were four reports of Bells palsy in the vaccine group and none in the placebo group," the report says. According to the analysis, these cases occurred at 3, 9, 37 and 48 days after vaccination. This side effect disappeared three days after it started in the participant who had this reaction three days after the vaccine. However, Bells palsy is still present in the other three volunteers. "With or without treatment, most patients make a full recovery (from Bells palsy) within a few months," reads the MSD Manual website.

Anti-Covid vaccine: significant allergic reactions occurred in two people

In recent days another side effect has been detected. These are serious allergic reactions. In the UK, two caregivers developed a severe allergic reaction on December 9 after injecting the anti-Covid vaccine from Pfizer and BioNTech. The two Britons, who had a history of acute allergic attacks, had to receive treatment quickly and are now better, British authorities said.

The UK Medicines Regulatory Agency has advised people with a history of severe allergic reactions not to receive this vaccine. This refers, according to the recommendation, to allergic reactions to other vaccines, drugs or even foods. British health authorities explain that this type of reaction is not so exceptional when a new vaccine is used.

Covid-19 vaccine: other side effects require a longer follow-up to be detected

"Once the vaccine is approved, its use in large numbers of people may reveal additional, potentially less frequent and / or more serious side effects that were not detected in the trial of 44,000 participants during the current monitoring period," say the Scientists from the Food and Drug Administration.

Experts from the US Agency for Medicines say that the available data do not indicate a risk of exacerbating the disease by vaccination and, conversely, confirm its efficacy against serious diseases within the available follow-up period. "However, the risk of vaccine-enhanced disease over time, potentially associated with waning immunity, remains unknown and should be evaluated in ongoing clinical trials and observational studies that may be conducted after authorization. "

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