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Explained: The possible allergic reactions associated with Pfizer Covid-19 vaccine

UK’s medicine regulator has issued an advisory warning against some of the possible allergic reactions to the Pfizer-BioNTech vaccine. What has it said? What are the allergic reactions recorded so far?

By: Explained Desk | New Delhi | Updated: December 15, 2020 3:19:00 pm
Pfizer vaccine, Pfizer vaccine allergic reactions, BioNTech vaccine, Pfizer vaccine news, Indian ExpressA nurse prepares a shot of the Pfizer-BioNTech Covid-19 vaccine at Guy's Hospital in London, Tuesday, Dec. 8, 2020. (AP Photo: Frank Augstein)

On Tuesday, the UK’s National Health Service (NHS) rolled out the biggest immunisation programme in its history when it administered the first dose of the Pfizer/BioNTech Covid-19 vaccine to a 90-year-old woman.

On Wednesday, the Medicines and Healthcare products Regulatory Agency (MHRA), UK’s medicine regulator, issued an advisory warning against some of the possible allergic reactions to the vaccine.

The warning came after two recipients of the vaccine reported anaphylaxis (a kind of allergic reaction involving swelling, hives, lowered blood pressure and in severe cases, shock) and one recipient reported a possible allergic reaction to the vaccine dose.

As per media reports, the two people who reported the allergic reaction have been treated and are okay now. According to the BBC, the two are understood to have a reaction called an anaphylactoid reaction, which involves skin rashes, breathlessness and sometimes a drop in blood pressure. This reaction is different from an anaphylaxis reaction, which can be fatal is not given immediate medical attention.

So what has the MHRA said?

The MHRA has said that any person with a history of immediate-onset anaphylaxis to vaccine, medicines or food should not receive the Pfizer/BioNTech vaccine. Further, those who experience anaphylaxis after the first dose should not receive a second dose, the regulator has said.

MHRA has also said that vaccine recipients should be monitored for 15 minutes after vaccination and that a protocol for the management of anaphylaxis and an anaphylaxis pack should always be available when the dose is being administered. “It’s very rare for anyone to have a serious reaction to the vaccine (anaphylaxis). If this does happen, it usually happens within minutes,” the NHS has said.

Other side-effects of the vaccine are expected to be mild and should typically not last longer than a week. These include a sore arm where the needle went in, fatigue, headache and feeling itchy. These side effects can be managed with painkillers such as paracetamol.

Are allergic reactions to vaccines common?

Reactions post-immunisations are common and as per the WHO, vaccine reactions can be classified into two groups: minor and severe. A vaccine reaction is an individual’s response to the properties of the vaccine. Minor reactions involving pain, swelling, redness at the site of the injection, fever, malaise, muscle pain, headache or loss of appetite usually occur within a few hours of receiving the injection and are resolved after a short period of time and pose “little danger” the WHO has said.

On the other hand, severe reactions do not result in long-term problems but can be disabling and are “rarely” life-threatening.

As per the WHO, “Anaphylaxis is a very rare allergic reaction (one in a million vaccinees), unexpected, and can be fatal if not dealt with adequately.” 📣 Follow Express Explained on Telegram

Who is eligible to get the COVID-19 vaccine in the UK?

At present, the NHS is offering the vaccine to people who are at the greatest risk of developing severe disease from COVID-19. These groups of people include those who are 80 years of age or over and already have a hospital appointment, people who work in care homes and health care workers at high risk.

How is the vaccine administered?

The vaccine called BNT162b2 is meant for individuals who are 16 years or older and is administered in two doses of 30 µg each, given 21 days apart. The vaccine is injected into the person’s upper arm and takes a few weeks after the completion of the second dose to work. “There is a small chance you might still get coronavirus even if you have the vaccine,” the NHS has said.

Data from clinical trials suggest that the vaccine is over 94 percent effective in adults over 65 years of age, which means that in a trial if 1,000 people are given the vaccine, about 60 are likely to be infected despite the vaccine compared to those in the placebo group.

Even so, those individuals who are vaccinated will still need to follow social distancing guidelines and wear masks since scientists are not yet sure if vaccinated people can still transmit the virus to others or not.

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