AstraZeneca ChAdOx1-S COVID-19 vaccine: no evidence of increased risk of anaphylaxis

Independent expert review of recently reported cases of suspected anaphylaxis following the AstraZeneca ChAdOx1-S COVID-19 vaccine has concluded that there is no increased risk of anaphylaxis associated with the vaccine above the expected rate for any other vaccine. Anaphylaxis is a very rare side effect that can occur with any vaccine.

The Therapeutic Goods Administration (TGA) convened a meeting of experts drawn from the TGA's Advisory Committee on Vaccines and the Australian Technical Advisory Group on Immunisation to review the individual cases in detail. The panel included medical experts in vaccine safety, infectious diseases, immunology, epidemiology and social science.

On Thursday 18 March 2021, the panel reviewed the five reports and information on two additional cases of suspected anaphylaxis following the AstraZeneca COVID-19 vaccine received by the TGA. Four reports came from Queensland and one from each of Victoria, NSW and Northern Territory.

The panel found that the information in only one of the reports met the required assessment criteria for anaphylaxis. This individual made a full recovery.

In considering the reports, the panel used the internationally-accepted Brighton Collaboration case definition of anaphylaxis. The Brighton Collaboration provides widely recognised methods for monitoring the safety of vaccines, developed by a group of global experts.

The panel advised that some of these cases may have represented allergic reactions or immediate stress responses to vaccination that may appear similar to an anaphylactic reaction, with symptoms such as nausea, throat tightness or rapid heart rate. Although they might not meet the criteria for anaphylaxis, they still need to be monitored and taken seriously.

In addition to the advice provided below in the statement published on 17 March 2021, which is still relevant and applicable, the TGA recommends that immunisation providers continue to provide adrenaline where they feel it is clinically required.

Learn more about the TGA's COVID-19 vaccine safety monitoring and reporting activities or how to report a suspected side effect.

Reports of anaphylaxis (severe allergic reaction)

17 March 2021

The Therapeutic Goods Administration (TGA) is closely reviewing reports of anaphylaxis after four cases were reported following the AstraZeneca ChAdOx1-S vaccine in the past 2 days in Queensland.

Anaphylaxis is a form of allergic reaction. It is a very rare side effect that may occur with any vaccine. The Australian Technical Advisory Group on Immunisation (ATAGI) advice emphasises that people without a previous history of specific or severe allergy should be observed post vaccination for the recommended 15 minute period. Only those with specific allergies or a previous history of anaphylaxis may require vaccination in a facility with medical staff in attendance, and to be observed for 30 minutes following administration of a COVID-19 vaccine dose. This advice can be found at: Clinical Guidance on use of COVID-19 vaccine in Australia in 2021 (v2.0) (pdf,515kb).

The TGA is conducting a comprehensive analysis of information from use of COVID-19 vaccines in Australia to date to confirm that the rate of anaphylaxis observed in Australia is consistent with the expected rate. This analysis includes:

• reviewing individual cases reported to the TGA to determine whether they are consistent with true anaphylaxis
• gathering information about whether the affected individuals have any history of allergy
• determining whether there is any clustering of common elements, such as location, batch, age or sex, that may require further investigation.

All of the Queensland reports related to vaccine from a single batch. TGA testing of the batch prior to release confirmed that it was compliant with all requirements. The TGA has confirmed that there were no temperature deviation for the batch during importation. TGA and UK have both conducted laboratory testing of the AstraZeneca vaccine prior to release as an extra safeguard. This testing has confirmed that the particular single batch of the AstraZeneca vaccine being used in Australia and administered at these Queensland sites is compliant with international standards, and is consistent with other batches of AstraZeneca vaccine supplied in Australia and safe to use.

A total of 183,006 doses of COVID-19 vaccine, including over 20,000 doses of AstraZeneca vaccine, have been administered to date in Australia. To 16 March, the TGA had received 19 reports of anaphylaxis nationally, 14 of which followed the Pfizer vaccine and 5 following the AstraZeneca vaccine. The AstraZeneca vaccine has been used in all states and territories.

This particular batch of AstraZeneca vaccine has been used extensively across the country with only one other suspected case of anaphylaxis across the entire nation.

Following the initial review the advice from TGA is the Astra Zeneca vaccine should continue to be administered as per the TGA-approved Product Information and following ATAGI advice.

Reporting problems

Consumers and health professionals are encouraged to report problems with medicines or vaccines. Your report will contribute to the TGA's monitoring of these products.

The TGA cannot give advice about an individual's medical condition. You are strongly encouraged to talk with a health professional if you are concerned about a possible adverse event associated with a medicine or vaccine.