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Study Shows That One Bavarian Nordic Shot Was 58% Effective Against Mpox.

• By Rich Health News Desk
• September 16, 2024

A single shot of one type of smallpox vaccine seems to cut the chance of getting mpox by about 60%, though this could be different for different types of the virus.

 

A type of mpox, which used to be called monkeypox, is spreading quickly in the Democratic Republic of the Congo. This is driven by a variant called clade Ib. The vaccines used to protect against mpox were first made for smallpox. Even though the two viruses are linked, it is not clear how well they work against mpox.

 

At the Institute for Clinical Evaluative Sciences in Toronto, Canada, Sharmistha Mishra and her colleagues looked into a vaccine called MVA-BN, which is also called JYNNEOS, Imvanex, and Imvamune. They did this to find out more. When mpox broke out in Western countries in 2022, this was the most common smallpox vaccine used. The clade IIb variety was to blame.

 

There is a huge range in how well MVA-BN works for mpox, from 36% to 86%, according to research. It's possible that this range is because the studies were observational and looked at the results of people of different ages, regions, and health.

 

Randomized control studies are being done with gay, bisexual, and other men who have sex with other men. These men made up most of the infections in Western countries during the outbreak in 2022.

 

In the meantime, Mishra's team has used available medical data to try to act like a randomized controlled trial. Over 6,000 Canadian men who were thought to have a high chance of getting an infection in 2022 were looked at by the researchers. About half had one dose of MVA-BN, and the other half had not had any mpox shots. Mishra says that the men in the two groups were matched based on things like age and where they lived.

 

Mishra says that the approved schedule for MVA-BN calls for two doses to be given at least 28 days apart. However, the Canadian government initially chose a single vaccine protocol to get doses to as many people who are at risk as possible.

 

Over a follow-up time of about 80 days, 21 men in the vaccinated group got mpox, compared to 50 men in the unvaccinated group. This means that MVA-BN lowered the risk by 58%.

 

If you only get this one dose, Adam Hacker at the Coalition for Epidemic Preparedness Innovations in London and Corine Geurts van Kessel at Erasmus MC in the Netherlands say it's enough to protect you. Hacker says, “scientifically, we know that two doses would have a higher efficacy,”

 

Geurts van Kessel says that the team's method was a good way to mimic a randomized controlled study. However, we don't know if any of the men in their mid-50s or older had been vaccinated against smallpox when it was still a threat, which could have changed how their immune systems responded to MVA-BN in 2022.

 

She also says that looking into how the vaccine might change how bad the illness is after getting mpox would help us figure out how well it works overall.

 

Geurts van Kessel says, "We also don't know how well it works against clade Ib". But she and Hacker both think that MVA-BN will work at least somewhat as well against this form as it does against clade IIb, which is still being spread in West and Central Africa.