A contraindication is a condition or situation that makes a medical treatment or procedure inadvisable because it could cause harm to the patient. For COVID-19 vaccines, the list of absolute contraindications is exceedingly small, meaning the vaccine is safe for the vast majority of the population. Understanding the difference between a condition that prohibits vaccination and one that simply requires a temporary delay or precaution is important. Official guidance clarifies who should not receive a vaccine, who should wait, and who can proceed without concern.
When Vaccination Is Absolutely Prohibited
The primary absolute contraindication to receiving a COVID-19 vaccine is a documented history of a severe allergic reaction, known as anaphylaxis, following a previous dose of any COVID-19 vaccine. A person who experienced this reaction should not receive any subsequent dose of that specific vaccine type. This prohibition also extends to individuals with a confirmed allergy to any component of the vaccine.
The main components causing concern are polyethylene glycol (PEG) and polysorbate. PEG is an ingredient found in messenger RNA (mRNA) vaccines, such as those made by Pfizer-BioNTech and Moderna, where it helps stabilize the delivery system. Polysorbate is found in some viral vector vaccines, like the Janssen (Johnson & Johnson) vaccine.
Since PEG and polysorbate are structurally related, an allergy to one may prompt evaluation before receiving a vaccine containing the other. A confirmed allergy to either PEG or polysorbate prohibits the use of any COVID-19 vaccine containing that specific excipient. If a person has a contraindication to one vaccine type, a healthcare provider may recommend an alternative vaccine that does not contain the problematic ingredient.
Temporary Delays and Situations Requiring Precaution
Some situations require a temporary delay or heightened caution, often referred to as a precaution, but do not prohibit vaccination entirely. A person currently experiencing a moderate or severe acute illness, such as one accompanied by a high fever or flu-like symptoms, should delay vaccination until recovery. This delay ensures that vaccine side effects are not confused with symptoms of the underlying illness.
A history of an immediate allergic reaction to any other vaccine or injectable medication (not containing PEG or polysorbate) is considered a precaution. Vaccination is not prohibited, but a medical professional should perform a risk-benefit assessment. The recipient is often observed for 30 minutes after the injection instead of the standard 15 minutes.
A person who recently received convalescent plasma or monoclonal antibodies for COVID-19 treatment was previously advised to delay vaccination. Current guidance has evolved, and a delay after receiving these antibody products is no longer necessary. However, the antibodies from the treatment might reduce vaccine effectiveness, so the decision to proceed should be made in consultation with a physician.
Individuals who have recently had a SARS-CoV-2 infection may also consider delaying a vaccine dose for up to three months. This delay is recommended because the increased time between infection and vaccination may result in a more robust immune response.
Conditions That Are Not Contraindications
Many common health conditions are not contraindications to receiving a COVID-19 vaccine and often make vaccination highly recommended. Individuals with underlying chronic medical conditions like diabetes, heart disease, lung disease, or hypertension should still be vaccinated. For these groups, the risk of severe illness from COVID-19 infection outweighs the risk associated with the vaccine.
A person with an immunocompromised status, whether due to a medical condition or immunosuppressive medications, can safely receive the vaccine because it is not a live-virus vaccine. Although the immune response may be less robust, vaccination is a primary defense against the severe consequences of infection. Pregnancy and breastfeeding status also do not prevent a person from being vaccinated.
Public health guidance recommends that pregnant people receive the vaccine, as they are at an increased risk for severe COVID-19 illness. A history of mild acute illness, such as a common cold or a minor fever, does not require a delay in vaccination. Allergies unrelated to vaccines, such as those to food, pets, environmental triggers, or oral medications, are not considered contraindications.