Vaccines and Allergies

As of this writing, New York state has administered more than three million first doses of the COVID-19 vaccine, which means that more than 12 percent of the state’s population has been inoculated, according to the Centers for Disease Control (CDC). Yet headlines of acute allergic reactions, such as anaphylaxis, to the vaccine often make the news; however, this can be misleading. In fact, according to the CDC, severe or life threatening allergic reaction appears to be very rare.

The two most prevalent COVID-19 vaccines at this time are manufactured by Pfizer and Moderna. They were authorized by the FDA for emergency use, and are deemed extremely safe. But if you’ve had a reaction before to a vaccine, such as the flu, what do you need to know?

First of all, providers administering the vaccine are trained to be prepared for allergic reactions. If there is an anaphylactic reaction that can be life threatening, because it constrict the airways or causes a drop in blood pressure, it usually occurs within the first 10 minutes of the inoculation, which is why you are asked to wait for at least 15-30 minutes before leaving.

If you’ve had an allergic reaction previously to any of the ingredients in the COVID-19 vaccine, which you can find on the CDC website, or have had related allergic reactions to the ingredient polyethylene glycol or polysorbate, you probably should not get it at this time. Additionally, if you’ve had a severe allergic reaction to a first dose, then you should probably avoid a second dose. However, if you are being treated for common allergies, such as seasonal or pet allergies, please know that the potential benefits from the vaccine clearly exceed the potential for harm and you are not excluded from receiving it.

In fact, sometimes people think they are having an allergic reaction because they feel sick from the vaccine, but this is the natural immune response from the vaccine that is actually supposed to happen. Symptoms such as low-grade fever, muscle aches, soreness at the injection site, fatigue and headaches can occur usually 12 hours after the vaccination, which signals that the immune system is developing and responding appropriately, and this is not an allergic reaction.

And even if you’ve had a severe allergic reaction in the past to another vaccine, it’s still possible to receive the COVID-19 vaccine under certain circumstances; where personnel is highly trained, and equipment and supplies are readily available to prevent or treat anaphylaxis.

Immune Response

For people who have compromised immune systems and are being treated for HIV/AIDS, cancer or organ transplants, or are taking corticosteroid medications, any vaccine may affect them differently. Inactivated vaccines use killed version of the disease germs. These include the flu vaccine, polio and hepatitis A and are delivered in doses as they are not as strong. Vaccines that use an activated, but weakened version of the germ are generally stronger and help build lasting immunity such as the measles, mumps, rubella and chickenpox vaccines.

Both the Pfizer and Moderna COVID-19 vaccines are neither inactivated nor activated. A new method using mRNA teaches cells to make a protein to trigger an immune response and create antibodies and in this way they are considered typically safe for people who are immunocompromised. The new Johnson & Johnson vaccine is a recombinant vaccine that is inactivated and uses a small piece of genetic material of the virus to trigger the immune response and is also usually considered safe for the immunocompromised. The J&J usually only requires one dose, whereas the mRNA vaccines usually requires two.

Keep in mind: the goal is to get the immune response. People with compromised immunity may be less likely to get the full response from the vaccines, so timing of the inoculation may be more important for them. For example, with HIV, the higher the T cell count the better in order to get a stronger response from the vaccine. If you are severely immunocompromised and are unable to receive the chickenpox vaccine or shingles vaccine for example, your physician may prefer that you don’t receive the COVID-19 vaccine until more clinical trials are performed on this population.

If you have any questions, make sure to speak with your doctor about the COVID-19 vaccines so you are prepared ahead of time when you become eligible and it becomes available to you. In the meantime, continue to wear a mask and social distance as much as possible.

Rachel L. Miller, MD is Chief of the Division of Clinical Immunology and Professor of Medicine for the Mount Sinai Health System.