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New bivalent BA.4/BA.5 COVID-19 booster vaccines well tolerated by Australians, new AusVaxSafety data show

New vaccine safety data published by AusVaxSafety have shown Australians report fewer side effects following COVID-19 vaccination with the newly introduced bivalent BA.4/BA.5 booster vaccines than with the existing bivalent BA.1 and original COVID-19 booster vaccines.

Bivalent – ‘bi’ meaning ‘two’ – refers to the number of antigens (i.e. SARS-CoV-2 strains) that are included in the vaccine. 

The two new bivalent vaccines (Moderna and Pfizer) now in use in Australia contain the Omicron BA.4/5 variant in addition to the original Wuhan strain. When administered, they therefore produce antibodies that target both of these strains, providing broader protection against newer variants currently circulating in the community. 

These new safety data have been released as part of the ongoing AusVaxSafety COVID-19 vaccine surveillance program.

AusVaxSafety received data from more than 27,000 Pfizer bivalent BA.4/BA.5 COVID-19 vaccine recipients (aged 12 years and older) and more than 3800 Moderna bivalent BA.4/BA.5 COVID-19 vaccine recipients (aged 12 years and older) who participated in active vaccine safety surveillance via the AusVaxSafety monitoring system.

Reassuringly, most participants experienced no side effects in the first three days following Pfizer bivalent BA.4/BA.5 (73 per cent) and Moderna bivalent BA.4/BA.5 (64 per cent) COVID-19 vaccination.  

Among those who did experience a side effect, local reaction (including pain, itching, redness and swelling at the injection site), fatigue, muscle/joint pain and headache were most common across both vaccines. 

These side effects were generally mild and short-lived, with most resolving within one day or less. Their impact on routine activities was low, with just four per cent of Pfizer bivalent BA.4/BA.5 respondents and seven per cent of Moderna bivalent BA.4/BA.5 respondents reporting missing work, study or routine duties in the week following vaccination. 

Reported medical attendance rates also remained low, at less than 0.3 per cent for both vaccines.


AusVaxSafety surveillance of all bivalent COVID-19 vaccines used in Australia is ongoing, and the latest vaccine safety data are published on the AusVaxSafety website fortnightly.

Access the latest Pfizer bivalent COVID-19 vaccine safety data here

Access the latest Moderna bivalent COVID-19 vaccine safety data here