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.”

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