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Omicron-specific boosters – Expert Reaction

The UK has become the first country to approve an Omicron-specific booster jab for Covid-19.

The recently approved vaccine, made by Moderna, targets two different coronavirus variants – the original virus from 2020 and the Omicron variant

The SMC asked experts about the announcement and what the data say so far about how effective they are.

Associate Professor Helen Petousis-Harris, Vaccinologist, University of Auckland, comments:

“The bivalent vaccines (both Moderna and Pfizer) have added the original Omicron BA.1 variant to the ancestral strain. Both induce neutralising antibodies to Omicron. However, there are few caveats to consider.

“These vaccines are likely to provide superior protection against the original Omicron BA.1 variant based on laboratory data, but of course the reign of BA.1 is essentially over and now we are in the era of BA.4 and BA.5, which are somewhat evasive to earlier Omicron immunity. Also, we do not yet have real world effectiveness data for these new formulations.

“Given what we know about Covid boosters in general, a second booster is of value to the very elderly and people who cannot make a good immune response to vaccines due to underlying conditions, but across the rest of the population there are diminishing returns. Currently, the existing vaccine we are using is doing a very good job of keeping people out of hospital and preventing deaths because the long-term immune memory is broad across many variants even when our antibodies have waned.

“Boosters are not starting from the beginning but rather they build on the existing immunity that we develop over months.”

Conflict of interest statement: “Helen Petousis-Harris has led studies funded by GSK and has provided expert advice to Pfizer and Merck. She does not receive any personal honoraria or funding.”

Peter McIntyre, Paediatrician, Medical Advisor to the Immunisation Advisory Centre, and Professor, Department of Women’s and Children’s Health, Dunedin School of Medicine, University of Otago, comments:

“The UK’s decision for rapid approval is understandable in the context of a rapidly approaching colder season, with the unknowns of influenza and Omicron looming and populations vulnerable to severe disease from either vulnerable to both. With respect to influenza, the Southern Hemisphere experience of flu resurgence will have been noted, while for Omicron there will be the desire to enhance the protection of those most vulnerable to severe disease prior to any resurgence during winter.

“However, the UK’s peak vaccine advisory committee, the JCVI, has emphasised that ensuring those eligible for a booster receive any approved Covid-19 vaccine is what is important, not the specific type of booster (including the new bivalent vaccine: Original Wuhan strain + Omicron BA1). This is because both the original vaccine and the new bivalent strengthen protection against severe disease, including that due to newer Omicron variants.

“Improved protection against any infection due to the predominant Omicron strain (BA5) now circulating in both NZ and the UK is much less certain than protection against severe disease. Based on antibody tests, some increase in protection against BA5 is expected from the BA1 vaccine and to some extent also from the Wuhan strain vaccine, but this is likely to be quite short-lived.

“With high rates of immunisation and prior infection, immunity is overall very high (>95%) in the UK and despite lower prevalence of prior infection also high in New Zealand. This means that the highest priority for New Zealand remains improving coverage of the third (first booster) dose in all adults (especially Māori and Pacific adults under 50 years, who are at higher risk and have the lowest coverage currently). Among adults at higher risk who had their first booster dose more than six months ago, maximising coverage of the second booster is important. Highest possible coverage of first and second boosters is much more important than any benefit from ‘variant-specific’ vaccines.

“By the time this becomes more relevant to New Zealand next autumn, it is very likely that Omicron will have further evolved, as will have variant specific vaccines and real-world data will be available on their performance.”

Conflict of interest statement: “The Immunisation Advisory Centre (IMAC) has a contract with the Ministry of Health to delivery education and training to the healthcare sector for COVID-19 vaccines. Professor McIntyre is a member of the Ministry’s COVID-19 Vaccine Technical Advisory Group and of the World Health Organisation (WHO’s) Strategic Advisory Group of Experts in Immunisation. This statement should not be taken to represent any policy position on the part of the Ministry or of WHO.”