Mpox Vaccine Protection Wanes Within A Year – Expert Reaction

Friday, 4 October 2024, 2:58 pm
Press Release: Science Media Centre

Immunity from the mpox vaccine Jynneos appears to drop off after a few months, and boosters may be needed, according to a small new study.

Researchers from Harvard Medical School found that mpox antibodies waned six to 12 months after immunisation, but that more research is needed to confirm this.

Last month, Te Whatu Ora reported 11 mpox cases in NZ linked to a Queenstown festival.

The SMC asked experts to comment.

Massimo Giola, President of the Australasian Sexual Health Medicine Committee of the Royal Australasian College of Physicians, comments:

“We have known for a while that the level of antibodies was going to drop over time after vaccination.

“But antibodies are not the only indicator of protection. There is also cellular immunity, which is extremely important for the protection against viruses.

“We also have had evidence that smallpox vaccines were protecting against mpox. Mpox only started to spill over from animals to humans in Africa after the universal smallpox vaccination was stopped.

“We are seeing internationally and even in the latest outbreak in New Zealand, cases of mpox among people who got the two doses of Jynneos vaccine. So it’s going to be a situation very much like the vaccine for Covid that essentially, particularly with the new variants, the vaccine doesn’t give you protection against infection. But it gives you protection against severe infection and death. So the cases of mpox among people who have had the vaccine are less severe and not leading to any serious consequences.

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“Therefore, even with study, it is crucial for people at risk to get two doses of the vaccine. That includes people who are immunosuppressed, or who have conditions potentially leading to immune suppression, such as those living with HIV, or people with cancer.

“There are no plans at the moment for further boosters, so watch the space if more evidence comes through.

“Finally the number of cases in New Zealand are so small that any detailed information such as geographical location can become identifiable. That is probably why public health officials are very careful about communicating the data.”

No conflict of interest declared.

Our colleagues at the UK Science Media Centre also gathered comments:

Dr. Alexis Robert, Research Fellow at the London School of Hygiene and Tropical Medicine, comments:

“This new research letter from Collier et al shows that Mpox antibody response declined with time since vaccination in 47 individuals vaccinated with the modified vaccinia Ankara–Bavarian Nordic. The antibody level after one year was back to the pre-vaccination levels for some of the Mpox antigens. The Mpox outbreak declared in the United Kingdom in 2022 was brought into control through declines in transmission rate from behavioural changes, and targeted vaccination of at-risk groups. The waning highlighted by Collier et al is therefore important to investigate, especially since vaccination of high-risk group was credited for reducing the risk of Mpox resurgence since 2022 (Brand et al, 2023).

“Mpox is an infectious disease associated with severe illness. To assess the current Mpox outbreak risks, we need to understand the level of immunity in the population. As highlighted by the authors, the study uses a limited sample size (25 1-dose recipients, 22 2-dose recipients), so the results need to be confirmed with larger, more representative samples, to get a full picture of the level of protection in the vaccinated population. In such a small sample, the effect of individual features cannot be analysed: for instance, the age at vaccination, or medical history could impact the response of individuals. Future analyses with larger sample size should identify factors that contribute to this decrease, so we better understand what it means for the level of immunity in the population.

“Finally, antibody concentration will need to be connected to infection risks through epidemiological investigations. This will show how vaccinated individuals contribute to outbreaks: are they as likely be infected as unvaccinated individuals? Are their symptoms milder? Are they as likely to transmit? If so, catch up campaigns may be needed to bring transmission risk down, and control Mpox outbreaks.”

No conflict of interest.

Dr. Boghuma Titanji, Assistant Professor of Medicine, Emory University, comments:

“This study is crucial as it examines individuals who received one or two doses of the MVA-BN vaccine or recovered from an mpox infection. The authors found that vaccine-induced neutralizing antibodies and T-cell responses declined significantly within 6-12 months. This raises concerns that previously vaccinated individuals may become more susceptible to mpox as their immunity wanes, suggesting that additional booster doses could be beneficial. Some countries, like the United Kingdom, are already recommending booster doses, though other nations have not yet updated their vaccination guidelines accordingly.

“It is reassuring that nearly two years after the peak of the mpox outbreak in North America and Europe, case numbers have remained low, and post-vaccine infections are rare. This suggests that immunity might not be solely dependent on antibody levels and that other immune factors not yet defined could still offer protection. While the findings need confirmation in larger cohorts including representation of key groups like pregnant people and children, they are important for guiding future vaccination strategies, especially for vulnerable groups at higher risk of exposure.

“Additionally, special attention must be given to understanding vaccine responses and immunity durability in immunocompromised individuals, such as those with HIV. This group is particularly vulnerable to severe mpox and poor outcomes, highlighting the need for tailored vaccination guidelines to protect them effectively.”

No conflict of interest.

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