A few hours ago, the image of the first person to have been administered the Pfizer / BioNTech vaccine against COVID-19 in the UK outside of a clinical trial was going around the world; One important point to underline is that before 90-year-old Margaret Keenan,about 44,000 people have been vaccinatedin order to ensure its efficacy and safety, as required in the pre-authorization process. Although this is good news, which some scientific disseminators have classified as historical, the administration of the long-awaited vaccine has been slightly clouded by a newsflash: the UK Medicines and Health Products Regulatory Agency (MHRA) has published a report detailing the situation of two workers from the British National Health Service (NHS), who reportedly manifested allergic reactions in response to the Pfizer / BioNTech vaccine.
Despite the relatively high number of people who had already received the vaccine in clinical trials, a greater number of people are exposed to the vaccine after authorization, so this expansion is expected to reveal possible adverse events that were not observed during trials, as is often the case with all drugs and vaccines.
As a precautionary measure, the MHRA has issued temporary guidance to the NHS wherebyrecommends not vaccinating those with a history of allergies, while conducting an investigation in order to fully understand each case and its causes. Of course, the news has alerted the population, and reluctant positions to the vaccine, or even denialists, have invaded social networks, generating distrust.
What does this ‘yellow card’ mean to the vaccine? Are there reasons to be concerned or are these reactions normal? Are only two cases – in the tens of thousands – enough to distrust a vaccine that is an achievement of modern science, and that can save lives and possibly recover the delicate global economic situation?
On the other hand, how have the allergic reactions of the two toilets been? Can they be considered serious? Are they enough to consider withdrawing their confidence in this vaccine?
While what happened is being clarified, the Science Media Center platform has gathered theopinion of various experts, in addition tocollect the events that have occurred, and put their seriousness and implications in context.
An anaphylactoid reaction to the vaccine
Let’s start by understanding what the allergic reaction experienced by the vaccine in these two people consisted of: these are anaphylactoid reactions, a response that presents some differences from anaphylaxis but which, in essence, are very similar. Saad Shakir, director of the Drug Safety Research Unit (DSRU), illustrates this to us: “An anaphylactic reaction is an allergic response of the body to external substances such as food, drugs and vaccines. Manifestations of anaphylaxis include effects on the cardiovascular, respiratory, gastrointestinal, and skin systems in the form of a severe rash. Blood pressure can drop and breathing can become difficult.
For this reason, he clarifies, people who are vaccinated are asked to stay at the vaccination site for a time to be monitored. Shakir continues: “However, the events that appear to have occurred after the Pfizer vaccine in these two people were anaphylactoid reactions, which are allergic reactions that share some of the characteristics of anaphylaxis , but are less severe. After the reaction, both were given the appropriate treatment ”.
And he adds: “Both anaphylaxis and anaphylactoid reactions and other allergic reactions are more likely to occur in people who have a history of allergies.” Hence the recommendation of the British health authorities.
Both reactions were treated and the affected people recovered well . Once this is cleared up, let’s move on.
Pfizer already included a warning on the label
This type of reaction is not entirely surprising to the laboratories developing the vaccine. Pfizer already included a statement warning that this vaccine should not be administered to “people with hypersensitivity to active substances.”
On the other hand, the two affected people had a history of allergy severe enough to require them to carry an adrenaline auto-injector, as Dr Penny Ward, Professor of Pharmaceutical Medicine at King’s College London explains: “These people would be at higher risk. to suffer an allergic reaction to a foreign compound compared to the population without a history of severe allergy ”.
On the label warning, Dr. Andrew Garrett, ICON’s executive vice president of scientific operations, elaborates: “The large clinical trial used to support MHRA approval of the vaccine already excluded those with a history of serious adverse reaction. associated with a vaccine or severe allergic reaction (eg, anaphylaxis) to any component of the study intervention ”.
A list of these components was included in the marketing authorization for the vaccine, but “it was not specific,” according to Dr. Shakir. From these two cases, this prescription has been updated: ” People should not be vaccinated if they have a history of allergic reactions severe enough to require adrenaline injection .” However, far from being disappointed, Professor Shakir is satisfied: “It is comforting that the decision was made and communicated so quickly.”
‘Those who are to receive the vaccine will have to be carefully questioned’
Understandably, there are individuals with little knowledge about their possible allergic susceptibility to the ingredients in a new vaccine. Therefore, the “precautionary principle” must be applied, Garret acknowledges: “As more data accumulates from both clinical trials and clinical practice, it is naturally expected that the safety profile will be updated and refined, as with any medicine ”, he concludes.
Labeling is very likely to expand in the future, but it would be wise to be careful in these early days “to avoid undermining public confidence,” Garret notes. In addition, he adds that – not only due to side effects, but mainly because the vaccine has a limited supply – it is necessary “to carefully question those who will receive the vaccine.”
The precautionary measure is sensible and conveys safety
Previous epidemiological studies of anaphylaxis suggest that an anaphylactic reaction could be observed within a community in up to 30 out of 100,000 inhabitants, approximately, or one in 3300 successive people over the course of a year, (according to a 2016 study).
Given that these two events occurred in people with a history of severe allergy , “it is sensible for the MHRA to draw attention to these reports and suggest that people with a history of severe allergy not get the vaccine for now,” notes Penny Ward.
But this should not alarm us. The MHRA is actively monitoring the safety of the vaccine during clinical use and is still expected to provide updates to clinicians as more information is gathered, as is often the case with all other drugs and vaccines.
What’s more: “The prompt notification of these events through the ‘yellow card’ scheme and the rapid issuance of additional information to guide practice shows that the security monitoring system is working well.”
Who should postpone getting this vaccine?
Many things can cause unexpected allergic reactions. In the words of Stephen Evans, professor at the London School of Hygiene and Tropical Medicine: “The allergic reaction occurs with quite a few vaccines and perhaps even more frequently with medications.” And he adds some interesting data observed during the clinical trial: “The data from Pfizer showed that about 0.6% of people had some type of allergic reaction in the vaccine trial, but about 0.5% showed it with the placebo. Therefore, there was a slight spike in allergic reactions with the vaccine, but it was small and the actual rate is unknown. “
Conclution
“What would be prudent, as the MHRA has already warned, would be for anyone who has known a severe allergic reaction who needs to carry an adrenaline autoinjector to postpone vaccination until the reason for the allergic reaction is clarified,” Evans recommends.
“But for the general population, this does not mean that we should be suspicious of receiving the vaccine, ” he ends.
