Should Americans with severe allergies avoid Pfizer’s coronavirus vaccine? Here's what we know so far

Moncef Slaoui, chief vaccine adviser for Operation Warp Speed, said he expected that the UK allergic reactions would be considered in the US authorization process


                            Should Americans with severe allergies avoid Pfizer’s coronavirus vaccine? Here's what we know so far
(Getty Images)

Two people in the UK suffered serious allergic reactions after receiving the new Pfizer-BioNTech Covid-19 vaccine, prompting regulators to warn those with a history of significant allergic reactions against having the inoculation. As the advisory panel of the US Food and Drug Administration (FDA) meets on December 10 to consider granting emergency use authorization (EUA) to Pfizer’s coronavirus vaccine candidate in the US, let us take a look at what do we know so far about the UK incidents and what does it mean for Americans?

What happened?

The National Health Service (NHS) workers are said to have developed symptoms of “anaphylactoid reaction” -- which may involve a skin rash, breathlessness, and sometimes a drop in blood pressure -- shortly after receiving the vaccine and both have recovered after treatment. Both have a history of serious allergies and carry adrenaline pens around with them. Such pens administer a swift adrenaline boost to counter allergic reactions. 

The Medicines and Healthcare products Regulatory Agency (MHRA) will investigate further and Pfizer and BioNTech will support their investigation. “We have been advised by MHRA of two yellow card reports that may be associated with allergic reaction due to administration of the Covid-19 BNT162b2 vaccine. As a precautionary measure, the MHRA has issued temporary guidance to the NHS while it conducts an investigation in order to fully understand each case and its causes,” stated Pfizer. 

According to the MHRA advisory, any person with a history of a significant allergic reaction to a vaccine, medicine, or food (such as previous history of anaphylactoid reaction, or those who have been advised to carry an adrenaline autoinjector) should not receive the Pfizer/BioNtech vaccine. The guidance also notes that vaccinations should only be carried out in facilities where “resuscitation measures are available.”

“As is common with new vaccines, the MHRA has advised on a precautionary basis that people with a significant history of allergic reactions do not receive this vaccination after two people with a history of significant allergic reactions responded adversely yesterday. Both are recovering well,” informed Stephen Powis, the national medical director for NHS England. 

What is the US saying?

The US Centers for Disease Control and Prevention (CDC) typically advises telling a provider if a person had had any severe or life-threatening allergies before taking any vaccine. 

According to the Medicines and Healthcare products Regulatory Agency in the UK, any person with a history of a significant allergic reaction to a vaccine, medicine, or food should not receive the Pfizer/BioNtech vaccine (Getty Images)

The Vaccines and Related Biological Products Advisory Committee (VRBPAC) of the FDA is expected to address concerns about the allergic reactions in the UK in its December 10 meeting, said chief vaccine adviser for Operation Warp Speed Moncef Slaoui. He indicated that Americans with known severe allergies may also be advised to not take the vaccine until more was understood, referring to the adverse reactions in the two British workers.

“Patients or subjects with severe allergic reaction history have been excluded from the clinical trials, which is classic. My expectation is that this is new news, and I would assume, but of course, the FDA will make those decisions, that tomorrow this will be part of the considerations. As in the UK, the expectation would be that subjects with known severe allergic reactions should not take the vaccine until we understand exactly what happened here,” noted Slaoui during a briefing on December 9. 

During an event, leading infectious disease expert Dr Anthony Fauci said that he was not very surprised as “these are the kinds of things that happen when you implement large vaccine programs,” but added that “it obviously is of some concern because there are people who have what’s called allergic diathesis or a tendency to get allergic reactions.”

“I believe that both of those individuals did in fact have that tendency...Remember we had 30,000 people in the Moderna trial and 44,000 people in the Pfizer trial. Once you start implementing the actual utilization of the vaccine in a clinical setting, you’re talking about millions of individuals getting vaccinated. So you may start seeing effects in some that might not have been picked up when you were dealing with thousands,” stated the director of the National Institute of Allergy and Infectious Diseases (NIAID).

Dr Fauci explained that the adverse reaction is “likely an unusual and rare effect.” But now that it is known, “we’ll be looking at that and particularly taking care of people who do have underlying allergic phenomenon, that they might be cautious about vaccination, or at least be prepared to respond with some sort of antidote to the allergic reaction.” He continued, “So if I were a person that had an underlying allergic tendency, I might want to be prepared that I might get a reaction and therefore be ready to treat it.”

Dr Fauci also pointed out that this is a good example of why it is important to have a variety of vaccine platforms. “So if in fact, we do find out that there is a consistent issue of certain subset of people like those with allergic reactions, you’ll always have other vaccine platforms that you can use and hopefully you will not see that with those other platforms," he added.

Did Pfizer’s trial report any adverse reactions among participants?

According to Pfizer’s clinical trial protocol, people with a “history of severe adverse reaction associated with a vaccine and/or severe allergic reaction (for example, anaphylaxis) to any component of the study intervention(s)” were not allowed to take part in the testing. 

The company said that in phase 3 clinical trial, the vaccine was “generally well tolerated with no serious safety concerns” as reported by the independent Data Monitoring Committee.

Dr Anthony Fauci said that the UK incidents were of some concern, but added that these are the kinds of things that happen when large vaccine programs are implemented (Getty Images)

 

What did the FDA analysis reveal?

A separate analysis published by the FDA revealed there were 10 cases of severe illness in the trial, with nine of those in the placebo group. “The total number of severe cases is small, which limits the overall conclusions that can be drawn; however, the case split does suggest protection from severe Covid-19 disease,” write authors. 

The FDA found slightly more adverse events “potentially representing allergic reactions” in its review of the Pfizer data. There were 137 “hypersensitivity-related” reactions to the vaccine, compared with 111 such events in the placebo group.

The most common adverse reactions were injection site reactions (84.1%), fatigue (62.9%), headache (55.1%), muscle pain (38.3%), chills (31.9%), joint pain (23.6%), and fever (14.2%). Severe adverse reactions were rare, most frequent after the second dose, and generally less frequent in adults 55 years and older (2.8%), as compared to younger participants (4.6%). The FDA concluded that there were no “meaningful imbalances” in serious health complications or adverse events, between the two (vaccine and placebo) groups. “Available safety data from all participants enrolled was consistent with the safety profile for approximately 38,000 participants with a median follow-up of 2 months,” they emphasized. In the group that received the vaccine, there were four cases of Bell’s palsy, temporary paralysis of facial muscles, but experts did not suspect a link to the vaccine.

What are other experts saying?

According to Stephen Evans, professor of pharmacoepidemiology at the London School of Hygiene & Tropical Medicine, allergic reaction occurs with several vaccines and perhaps even more frequently with drugs, so the UK incidents were not unexpected. “What would be wise, as the MHRA have already advised, would be for anyone who has known severe allergic reaction such that they need to carry an EpiPen, to delay having a vaccination until the reason for the allergic reaction has been clarified. For the general population, this does not mean that they would need to be anxious about receiving the vaccination. One has to remember that even things like marmite can cause unexpected severe allergic reactions,” he explained. 

Professor Peter Openshaw, past-President of the British Society for Immunology and Professor of Experimental Medicine at Imperial College London, noted that as with all food and medications, there is a “very small chance” of an allergic reaction to any vaccine. “However, it is important that we put this risk in perspective. The occurrence of any allergic reaction was one of the factors monitored in the phase 3 clinical trial of this Pfizer/BioNTech Covid-19 vaccine, the detailed data from which was released. In this, they reported a very small number of allergic reactions in both the vaccine and placebo groups (0.63% and 0.51%),” emphasized Openshaw. He added, “The fact that we know so soon about these two allergic reactions and that the regulator has acted on this to issue precautionary advice shows that this monitoring system is working well.”

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