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Omicron-specific vaccine approved for over-30s – Expert Reaction

Everyone in Aotearoa over 30 years old will be able to get the new Pfizer Covid-19 bivalent vaccine from the beginning of April.

The bivalent vaccine uses components of two strains of the virus – the original strain of Covid-19, and the Omicron variant, which is causing most Covid infections in Aotearoa currently.

The SMC asked experts to comment. 

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

“Procurement of a bivalent Covid-19 vaccine is a logical move at this stage of the pandemic but these vaccines are not game-changers.

“The bivalent Covid-19 vaccine includes the original variant that first appeared in Wuhan (the ancestral strain), as well as a more recent variant related to the Omicron family. The idea is that it will provide superior protection over the original monovalent (single) vaccine that most people have already received by presenting additional SARS-CoV-2 diversity to the immune system.

“The bivalent booster vaccination does appear to have an edge over the single-valent version, but not an awful lot. It has shown benefit in reducing infections and hospitalisations, and has greatest impact in those at increased risk, including elderly people and those with a medical risk condition.

“It is important to note that there is limited added protection of bivalent vaccination in preventing Omicron infection in people who have received primary vaccination and one or two monovalent booster vaccinations. Especially in persons with prior Omicron infection. It should be noted that studies on the effectiveness do not tend to compare the effectiveness of bivalent with monovalent boosters, they compare bivalent boosters with no booster. Key message – get a booster if you want to maximise protection.

“When we talk about how effective these newer vaccine formulations are, we are often comparing people who have received at least three doses of vaccine and had an infection with those who have also received a bivalent booster rather than completely unvaccinated uninfected people, so things become relative. Key message, a booster, particularly a bivalent booster, can curb infection for a short time. It contributes most additional value to prevention of severe disease in older people and those with high risk conditions.”

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.”

Professor Michael Plank, Te Pūnaha Matatini and University of Canterbury, comments:

“It’s excellent news that bivalent booster vaccines will be available to all over 30s from 1 April. For the many people whose last vaccine dose or infection was several months ago, this will give an important boost to our immunity against Covid-19. This move brings us more into line with Australia, where the bivalent booster is recommended for over 65s and available to all over 18s whose most recent vaccine dose or infection was more than 6 months ago.

“Vaccines train our immune system, a bit like showing it a photo of the virus so it can recognise the real thing when it comes along. Unlike the original Pfizer vaccine, the bivalent booster contains an Omicron-specific component. Although it’s not exactly the same as the currently circulating variants, it’s like a photo of the virus’s twin brother or sister rather than a distant cousin. This means our immune system will be better prepared to fight off current variants and future variants that are likely to be closely related.

“The timing of the rollout makes sense as it means people will have maximum immunity as we head into winter when Covid-19 is likely to spread more easily. Flu is also a major cause of vaccine-preventable illness and death during winter months, so it’s great that people will be able to get their Covid and flu vaccines at the same appointment.”

Conflict of interest statement: “I receive funding from the Department of Prime Minister and Cabinet and the Ministry of Health for mathematical modelling of Covid-19.”

Associate Professor Dianne Sika-Paotonu, Immunologist, Associate Dean (Pacific), Head of University of Otago Wellington Pacific Office, and Associate Professor, Dean’s Department, University of Otago Wellington, comments:

“This is welcome news given that although we’re in the middle of summer here in Aotearoa New Zealand, we’re continuing to experience impact of Omicron and people are still getting sick. We’ll be moving into winter in a few months’ time, with future Covid-19 waves still likely.

“The newer bivalent Covid-19 boosters, contain mRNA coding for the original virus strain (giving broad protection against COVID-19), plus an mRNA code common between the Omicron variant BA.4 and BA.5 lineages (giving better protection against Omicron specifically).

“A number of Omicron subvariants are currently in circulation here in Aotearoa New Zealand we are still learning about the newer ones emerging. One of the latest is “Orthrus” otherwise known as CH1.1. (an offshoot of Omicron subvariant BA.2.75) and has potential growth advantage over some of the other subvariants. “Orthrus” is named after the 2 headed dog in Greek mythology killed by Hercules). XBF is another of the recent Omicron subvariants in circulation here in Aotearoa New Zealand.

“New variants of the SARS-CoV-2 virus will continue to emerge, develop and spread, while issues with unequal global Covid-19 vaccine coverage, availability, accessibility and distribution persist, and remain unaddressed. Addressing health inequities and current inequities in society will be critical steps moving forward.

“Simple public health measures include being up-to-date with vaccines and boosters, isolating when sick, testing, wearing a mask where possible, proper ventilation, and being outdoors. These remain important steps to help protect against the most severe impacts of Covid-19, help protect against reinfection, and also help protect against other illnesses still circulating at this time.”

No conflicts of interest declared.

Professor Nikki Turner, Director Immunisation Advisory Centre, University of Auckland, comments:

“Evidence continues to clearly show the effectiveness of a course of the mRNA Comirnaty Covid-19 vaccine against severe disease, but it is relatively less effective for mild disease or transmission. So many vaccinated will still catch Covid, but most will avoid severe disease.

“The virus has evolved from the original strains through to a range of Omicron strains. It is clear that for all adults, a primary course of two doses, plus a booster, is needed to reduce the risk of severe disease – i.e. being hospitalised or dying from Covid disease. The vaccine does have some effect against mild disease and reducing transmission – but to a lesser extent, and it is this protection that wanes fairly fast. There are still a lot of people who haven’t had their first booster and for healthy adults we should concentrate on getting that first booster, as a priority.

“For healthy adults, two vaccine doses plus having one booster (2 + 1) is important protection against Omicron strains. Having mixed immunity is good too, that is, for people who have had vaccinations and then also had Covid infection. Even if it’s many months from the first booster shot, for most people protection from severe disease continues.

“Further boosters are recommended and are shown to have effectiveness, particularly for people at higher risk, the elderly or those with other health problems, i.e. when their immune systems are compromised in some way. The extra booster helps them to lift their immunity so it’s closer to that of a healthy person with a first booster.

“Bivalent vaccines for Covid (that include a component of the original strain of Covid and an Omicron strain) have been tested internationally. The results to date do show a good immune response that has the potential to offer even broader protection than the current ‘monovalent’ vaccine.

“So far the research done in the United States and Israel suggests that the use of a bivalent vaccine as a further booster can reduce hospitalisations in those 65 years and older by 73 to 84% (compared with no booster). They are also expected to be effective against recent strains of the Omicron subvariant XBB, which is dominant in the United States now.

“An Israel study including 700,000 participants showed 81% reduction in hospitalisations and 86% reduction of deaths using the bivalent vaccine in adults 65 years and older, while data from the CDC in the United States in November shows a 13.5-fold reduction in hospitalisations for adults 65 years and older who received a further bivalent booster versus those who were unvaccinated. There was a 2.5 fold higher rate among seniors vaccinated but without a bivalent booster.

“A range of cohort studies in the US have demonstrated a relative improvement in effectiveness of booster doses against severe COVID-19 when bivalent vaccines are given, especially for older adults who received two to four previous doses several months prior. One study found that the bivalent booster was 36.9 percent more effective against hospitalisation or death due to omicron variants than a monovalent booster.

“There is a clear body of consistent evidence now to show the bivalent’s benefit in a booster dose particularly for high risk individuals, and there is nothing to suggest the bivalent is inferior. All data points to added benefit.”

Conflict of interest statement: “Professor Turner is a member of the PITAG immunisation subcommiteee to Pharmac; Chair of NVC – the measles national verification committee for the Ministry of Health; a member of the CVTAG – COVID-19 Technical Advisory Group to the Ministry of Health; and a member of PHEAG – Strategic COVID-19 Public Health Advisory Group to the government. The Immunisation Advisory Centre (IMAC) has a contract with the Ministry of Health to deliver clinical advice, promotion, education and training to the healthcare sector for the national schedule vaccines and COVID-19 vaccines.”