Sun, 02/26/2023 | News

What is a bivalent COVID-19 vaccine and how do the short-term side effects compare to the original COVID-19 booster vaccines?

Australia has relied on a number of COVID-19 vaccines to successfully protect the population throughout the COVID-19 pandemic. While these vaccines are still highly effective in preventing severe disease associated with COVID-19, research has shown that the initial course of COVID-19 vaccination may provide more limited protection against symptomatic disease caused by the Omicron variant.

To counter this, bivalent COVID-19 booster vaccines have been developed that trigger an immune response against multiple COVID-19 variants to provide broader protection.      

With bivalent COVID-19 vaccines now in use in Australia and additional updated bivalent COVID-19 vaccines having recently been approved by regulators for future use, let’s take a look at the safety of bivalent COVID-19 vaccines and who should receive the vaccine. 

What is a bivalent COVID-19 vaccine and how does it differ from original COVID-19 vaccines?

The original COVID-19 vaccines – Pfizer, Moderna, Novavax and AstraZeneca – are monovalent vaccines (‘mono’ meaning ‘one’) and contain only the original Wuhan strain of SARS-CoV-2, the virus that causes COVID-19. When administered, they produce antibodies that target the original Wuhan strain. 

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

Bivalent mRNA vaccines (Moderna and Pfizer) contain both the original Wuhan strain alongside the Omicron BA.1 or the Omicron BA.4/5 variant. When administered, they produce antibodies that target both the original Wuhan strain and the Omicron BA.1 or Omicron BA.4/5 SARS-CoV-2 variant to provide broader protection against newer variants currently circulating in the community.  

Which bivalent COVID-19 vaccines are available in Australia and who should get vaccinated?

There are currently three bivalent COVID-19 vaccines approved for use in Australia: 

Pfizer Bivalent Original/Omicron BA.1 COVID-19 vaccine
Individuals aged 18 years and older who are eligible for a booster dose are able to receive the Pfizer Bivalent Original/Omicron BA.1 COVID-19 vaccine. 

Moderna Bivalent Original/Omicron BA.1 Bivalent COVID-19 vaccine
Individuals aged 18 years and older who are eligible for a booster dose are able to receive the Moderna Bivalent Original/Omicron BA.1 COVID-19 vaccine. 

Pfizer Bivalent Original/Omicron BA.4/BA.5 COVID-19 vaccine – Stock expected March 2023
Individuals aged 12 years and older who are eligible for a booster dose are able to receive the Pfizer Bivalent Original/Omicron BA.4/BA.5 COVID-19 vaccine.

An additional bivalent COVID-19 vaccine – Moderna Bivalent Original/Omicron BA.4/BA.5 COVID-19 vaccine – has recently been granted provisional approval for use in Australia by the Therapeutic Goods Administration (TGA). The potential use of this vaccine in the national COVID-19 vaccination program is still to be determined, with the Australian Technical Advisory Group on Immunisation (ATAGI) likely to provide advice to Government in the near future.  

What are the likely side effects from bivalent COVID-19 vaccines?

Like most medicines used in healthcare, vaccines can have side effects, also known as adverse events following immunisation (AEFIs). These side effects are usually mild and temporary. 

AusVaxSafety received data from more than 5,400 Moderna bivalent COVID-19 vaccine recipients and more than 2,500 Pfizer bivalent COVID-19 vaccine recipients who participated in active vaccine safety surveillance via the AusVaxSafety system.

Active surveillance data published by AusVaxSafety show more than half of the participants experienced no side effects in the first seven days following Moderna bivalent (53%) and Pfizer bivalent (65%) 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 are known to occur after these vaccines. They were generally mild and short-lived, with most resolving within one day or less. 

The rate of impact on routine activities was low, with 13% of Moderna bivalent respondents and 8% of Pfizer bivalent respondents reporting missing work, study or routine duties in the week following vaccination. The vast majority of respondents reported missing one day or less. Reported medical attendance rates also remained low, at less than 0.5% for both vaccines.

How does the side effect profile compare to the original COVID-19 booster vaccines?

Early data suggest that Moderna bivalent and Pfizer bivalent COVID-19 vaccines are better tolerated than the original Moderna and Pfizer COVID-19 booster doses, with lower rates of side effects, medical attendance and impact on routine activities reported by AusVaxSafety participants following bivalent COVID-19 vaccination compared to original COVID-19 vaccination.

What is being done to monitor the safety of bivalent COVID-19 vaccines in Australia?

Australia has one of the most robust vaccine safety monitoring systems in the world. The TGA will be monitoring any reports of serious AEFIs following bivalent COVID-19 vaccination via its passive reporting system.

AusVaxSafety is also actively monitoring the adverse event profile and safety of Pfizer and Moderna bivalent COVID-19 vaccines to ensure that they are performing as safely as expected in real-world conditions, with bivalent COVID-19 vaccine safety data updated on the AusVaxSafety website fortnightly.

Access Pfizer bivalent COVID-19 vaccine safety data here

Access Moderna bivalent COVID-19 vaccine safety data here
 

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