DENVER — After two healthcare workers experienced an allergic reaction from the Pfizer COVID-19 vaccine, Britain regulators are warning individuals with a history of severe allergic reactions against receiving the vaccine.
"First, this is not unexpected. We know virtually any vaccine, any medicine can cause an allergic reaction," Dr. Thomas Campbell of UCHealth told 9NEWS.
"It is not uncommon. Medications and vaccines can cause adverse reactions, but that doesn't necessarily mean we don't get vaccinated," said Dr. Shaila Gogate, an allergist and medical director for the Colorado Allergy and Asthma.
We took our questions about the news out of Britain to both physicians who urged people to remain levelheaded and trust the scientific process.
(Editor's note: Responses have been edited for context and clarity.)
9NEWS: What do you know about the warnings out of the UK for people with a history of severe allergic reactions?
Dr. Thomas Campbell, infectious disease physician for the CU School of Medicine: "Two health care workers who received the Pfizer COVID vaccine had severe allergic reactions. These are reactions that we call anaphylaxis. It's the most severe form of an allergic reaction, usually occurring within minutes after exposure to whatever the substance is. It can occur with many different things including peanuts, for example. Typically, people who have this type of allergy are people who carry a common device called an epi-pen so they can administer it promptly. Both of the individuals who had this reaction to the Pfizer vaccine had a past history of severe allergic reactions. In the UK, the medical authorities are advising people who have that type of past history, not to receive the vaccine."
Dr. Shaila Gogate, allergist and medical director for the Colorado Allergy and Asthma Centers: "We've had a few phone calls in regards to patients wondering if the vaccine would be safe for them because obviously, we see many patients with significant allergic reactions. In the UK, there were two health care workers that reported having an anaphylactic reaction after receiving the vaccine but thousands of people received the vaccine in Britain yesterday. The short of it is, we don't really know how things are going to play out at this point. I think there's more information that's going to be gathered. I'm telling my patients that are calling to just sit tight and see how things play out."
Is this unusual for a new vaccine?
Dr. Campbell: First, this is not unexpected. We know virtually any vaccine, any medicine can cause an allergic reaction. Some people are much more prone to that than others. Fortunately, it seems to be very rare. I don't know how many doses they administered in the UK yesterday, but only two people had this reaction and, as I mentioned, they were both individuals who had a previous history of severe reactions. I don't think people should be alarmed by this and I don't think this should interfere with receipt of coronavirus vaccines unless it's for someone who has that type of severe allergy history.
Dr. Gogate: It is not uncommon. Medications and vaccines can cause adverse reactions but that doesn't necessarily mean we don't get vaccinated. We have to take things in a measured way and get the vaccinations in the proper health care settings if it is appropriate. That's something each person's physician can decide when the time comes.
What about the vaccine may cause an allergic reaction?
Dr. Campbell: We don't know. The Pfizer and Moderna COVID vaccines are what we call messenger-RNA based. The messenger-RNA is the main component of the vaccine and does not elicit much in the way of an immune response. So, it's probably not the RNA component. There are other things mixed in to stabilize the vaccine and to enhance the uptake of the RNA once the vaccine is injected into our shoulder muscle. It's probably a reaction to some of those other components of the vaccine.
People who have these types of histories were not allowed to enter the trials for the very reason they might have a bad, bad reaction. People who have this type of history, often have a component of their immune system which is overactive and responds more intensely to external stimuli or external things coming into the body. They can then be at increased risk for any new thing that comes along, triggering a severe allergic reaction.
What will this mean for those who receive the vaccine moving forward?
Dr. Campbell: We learn a lot from studying vaccines in clinical trials. Both the Pfizer and the Moderna clinical trials were very large. Pfizer enrolled, approximately 45,000 participants. Moderna enrolled 30,000. In both cases, half of the individuals got a vaccine. In the case of the Pfizer vaccine for example, if, say roughly 22,000 people got the vaccine in the phase three trial, with that number of individuals we're not going to detect very rare events. So, if an event is occurring at a very low frequency, one in 100,000, we're probably not going to detect that in a sample of 22,000 people. As we're giving the vaccines to hundreds of millions of people, we will be able to see if other rare events like these allergic reactions occur and were not detected in clinical trials. It's important that as the vaccines are used that measures are in place to safeguard patients against these type of reactions.
In addition to advising people with a history of anaphylaxis not to get the vaccine, it's also important the vaccine be administered in a medical setting where there are trained personnel with the equipment necessary to provide treatment should a severe allergic reaction occur. It's probably also going to be necessary for patients to remain under observation for some period of time after getting the vaccine in the event an allergic reaction develops.
Do you expect this to impact uptake rates of the vaccine at all?
Dr. Campbell: I don't think this will have any significant impact on the vaccine distribution or our ability to get sufficient levels of vaccination in the community. The frequency of individuals having such severe allergic reactions is very low. It's not going to detract from the efforts to use these vaccines to get the COVID pandemic under control.
Dr. Gogate: I would ask folks to continue to social distance and continue to wear a mask. Vaccines are effective when we vaccinate. Let's just take our time. As the FDA approves this product, I'm sure there'll be information that comes out in regards to safety. Let's not make a judgment before we have all the facts.
What does this mean for the safety of the vaccine?
Dr. Campbell: This does not mean that the vaccine is unsafe. This is something we expect from any vaccine and from any medication. We will learn lessons along the way and the lesson learned here is people need to be cautioned, not to receive the vaccine if you have that type of past history. So, this does not mean the vaccine is unsafe for the other 99.9% of the population.
Dr. Gogate: With regards to the history of severe allergic reactions, I think we wait and see what actually comes up. It's too soon to say at this point. Having said that, I want to be vaccinated, I will get vaccinated. I think it's the right choice to make. As a health care provider, I have a lot of patient-facing encounters and I want to make sure I'm protecting my patients. So, when available, I will get vaccinated. This news, it's very early, it's two patients out of thousands hat were vaccinated. Thousands were vaccinated. It is simply too soon to say that it is unsafe. We just don't have the facts.
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