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What adverse reactions can occur with the COVID-19 vaccines?

What advice can you give patients who may be concerned about the adverse effects of the COVID-19 vaccines?

Unplanned learning

This article was correct at time of publishing (February 17). For further news and updates please visit C+D’s COVID-19 hub

As the COVID-19 vaccination programme is now being rolled out in the community, it is important that pharmacists and the pharmacy team are equipped with the knowledge to inform patients about the safety of the vaccines. Vaccination is the best preventative method against COVID-19 – although social distancing measures should still be followed – to avoid more fatalities and hospital admissions.(1)

What are the most common adverse side-effects?

For most vaccinations, mild to moderate side effects are normal. The Medicines and Healthcare products Regulatory Agency (MHRA) has reviewed the safety information of both vaccines in clinical trials involving more than 44,000 paticipants for the Pfizer/BioNTech vaccine and more than 23,000 participants for the Oxford/AstraZeneca vaccine.

The MHRA concluded that side effects commonly occured within seven days of receiving the vaccine and were mainly mild or moderate. The side effect profile was similar for the two vaccines. The most frequent adverse reactions in trials included pain at the injection site, chills, fatigue, muscle aches and headaches – although these commonly resolved 1-2 days post-injection. These reactions reflect the normal immune response triggered by the body following vaccination and are common with most types of vaccine.(2-4)

These adverse effects were reported in more than one in 10 people for both vaccines. For the Pfizer/BioNTech vaccine,adverse reactions were reported less frequently in older adults (over 55). For the Oxford/AstraZeneca vaccine, adverse reactions after the second dose were milder and reported less frequently than after the first dose. Adverse reactions to this vaccine were generally milder and reported less frequently in older adults (65 years and older).(2-4)

Patients should be advised to still get the second vaccine dose, even if they experienced some symptoms following the first dose.(3) Patients should also be advised that neither approved vaccine is using a live SARS-CoV-2 virus; therefore it is not possible to get COVID-19 from the vaccine.(4)

Reassuring patients who worry about severe reactions

Out of the 44,000 participants in the Pfizer/BioNTech COVID-19 vaccine trial and the 23,000 participants in the Oxford/AstraZeneca trial, there were no recorded severe reactions to the vaccine.(4) It is important to reassure patients that the MHRA assessed the safety profile for both the vaccines, as well as their efficacy, before rolling out the vaccines to the general public.(4)

On December 9, there were two cases where vaccine recipients who had history of significant allergies suffered serious reactions to the Pfizer/BioNTech vaccine. The MHRA issued a warning stating that people should not receive the Pfizer/BioNTech vaccine if they had a history of anaphylaxis to a vaccine, medicine or food. On December 30, the MHRA issued updated guidance after reviewing further data that showed that severe allergic reactions are very rare (less than 1 in 10,000 people receiving this vaccine). The updated guidance states that the Pfizer/BioNTech vaccine should not be administered to people with a previous history of severe allergic reactions to any ingredients of the vaccine, but that it can now be given to those with other allergies – such as food allergies. The Green book has also been updated to reflect this update.(4,5)

For more information on the guidance for patients with allergies, read C+D’s article on the latest COVID-19 vaccine recommendations.

Why is yellow card reporting important?

Yellow Card reporting is important for the MHRA to have the most up to date information on the safety of medicines in public use. As the regulator, the MHRA continually monitors safety during widespread use of the vaccines. Using the Yellow Card Reporting Scheme, any health professional or member of the public can submit suspected side effects. However, it is important to note that some Yellow Card reports might not reflect proven side effects but may  may have occurred coincidentally without any link to the vaccine.(4,6)

What does the evidence say so far?

In the most up-to-date safety report for both vaccines (at the time of publication, February 17), the overall reporting rate is roughly 3-4 Yellow Cards per 1,000 doses administered.(4) For both vaccines, the overwhelming majority of reports relate to mild injection site reactions and generalised symptoms such as “flu-like” illness, headaches, chills, fatigue, nausea fever, dizziness, weakness, aching muscles, and rapid heartbeat. Generally, these happen shortly after the vaccination and are not associated with more serious or lasting illness.(4)

The report states that:(4)

  • So far, the general safety experience with both vaccines is as expected from the clinical trials.
  • At present, the expected benefits of both vaccines in preventing COVID-19 and serious complications (including hospital admissions) are much greater than the risk of side effects from the vaccine.

As they are rolled out across the UK, members of the public should be assured that the vaccines will be continuously monitored and evaluated by the MHRA and that public health bodies and guidance will be updated as more data becomes available.

As pharmacy professionals, you should seek to reassure members of the public that vaccination is the single most effective way to reduce deaths and severe illness from COVID-19, when they approach you for advice.

  1. NHS (2021) Coronavirus (COVID-19) vaccine
  2. Centers for Disease Control and Prevention (2020) Information about the Pfizer/BioNTech COVID-19 vaccine
  3. University of Oxford (2020) Vaccine knowledge project, COVID-19 vaccines
  4. Medicines and Healthcare products Regulatory Agency (2021) Coronavirus vaccine - weekly summary of Yellow Card reporting
  5. Public Health England (2021 COVID-19: The green book, chapter 14a
  6. Specialist Pharmacy Services (2021) COVID-19 vaccines in development
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