How Well Does the Monkeypox Vax Work? No One Knows for Sure

Across a gay community of American men worried about catching monkeypox, one message suggests it’s all temporary: A few months of sex care and vaccination will usher in a carefree fall.

“For your safety and to spare you the horrors of this disease,” sex columnist Dan Savage suggested on Twitter last weekend, “you might want to think maybe you could call him back in a few weeks while we get the vaccine out.” AIDS Journal save recommends that readers “stick to a slow summer” and wait for the fall, when “we hope to have enough Jynneos vaccine for all who want it.”

However, no one knows how well the Jynneos vaccine will serve as a way out of the infection.

A number that has been quoted without question by various media organizations – “85% effective” or “at least 85% effective” – ​​is based entirely on a small study done in Africa in the 1980s that has major limitations. One data expert calls his findings “very weak.” Other studies have only been conducted in animals.

However, “I’ve heard from a lot of people in the community that they expect almost no risk of getting infected 2 weeks after their first shot,” said Michael Donnelly, MSc, a New York City data scientist and LGBT health advocate, in an interview with MedPage Today. “Or they think they won’t have any symptoms if they were exposed before the injection.”

The lack of accurate information about the vaccine is “a huge problem,” Jay Varma, MD, director of the Cornell Center for Pandemic Prevention and Response in New York, said in an interview. “It is absolutely critical that public health officials work to get the message of this uncertainty across to people getting vaccinated.”

Vaccine assumptions based on small, ‘weak’ 1988 study

As of July 29, the CDC reports that the current outbreak has caused 5,189 infections in the US, hitting nearly every state (all but Montana, Wyoming and Vermont) plus Puerto Rico. New York is by far the most affected with 1,345 cases, followed by California with 799, Illinois with 419, Florida with 373, and Texas and Georgia with 351 each. There is a particularly high per capita rate in Washington DC, with 218 cases in a city of 702,000.

Men who have sex with men are considered the most vulnerable — they accounted for 98% of 528 cases worldwide in a recent analysis — and many gay men have taken to social media or spoken to reporters to describe pain strong, terrible lesions and barriers to take care of.

Hundreds of thousands of Jynneos monkeypox vaccines are now available in the US, and the CDC recommends vaccination for those who have been exposed to monkeypox or are at higher risk.

Health officials prefer the Jynneos vaccine, which is made by the Danish company Bavarian Nordic and approved by the FDA to prevent both smallpox and monkeypox. An alternative vaccine, ACAM2000, is complicated to administer, produces a nasty, infectious rash and can cause side effects in some people, such as those with weakened immune systems, according to Vox.

As the CDC notes, “no data are yet available on the effectiveness of these vaccines in the current outbreak.” As for previous outbreaks, only one study — a retrospective analysis published in 1988 — has examined whether a smallpox vaccine can prevent monkeypox.

In that study, researchers tracked household contacts of 209 people infected with monkeypox in Zaire in the early 1980s. Those with signs from previous smallpox vaccination (70%) were 85% less likely to become infected. The vaccine appeared to be 89% effective in protecting non-household contacts from infection.

The statistical analysis is limited because there is no confidence interval or adjustment for factors such as age, said Ira Longini, PhD, a biostatistician at the University of Florida. MedPage Today. Also, he said, the data is based purely on physical signs of vaccination. The study “is the only piece of evidence we have [in regard to vaccine effectiveness], which is quite weak. In principle it should work, but we don’t know.”

Jynneos and ACAM2000 are newer generations of vaccines like Dryvax that were used in the 1980s. “These vaccines have not been directly tested against smallpox or smallpox,” said Richard Kennedy, PhD, co-director of the Mayo Vaccine Research Group in Rochester, Minnesota. , in an interview with. MedPage Today. “The immune responses they create are very close to first- or second-generation vaccines: a little weaker, but not much.”

Kennedy added that vaccines have also been tested against monkeypox in five to 10 different animal studies. “These data are also clear and consistent with very good protection against disease with animals showing little or no disease symptoms after challenge,” Kennedy said. “The animal data were strong enough that the FDA approved Jynneos to be licensed for the prevention of monkeypox.”

Unique spread can weaken the effects of the vaccine

To make matters more complicated, the new outbreak is quite different from those in the past. This time, the virus appears to be transmitted primarily through sexuality rather than other contact, with the vast majority of cases among men who have sex with men. (There is now a debate in the medical world whether monkeypox should be referred to as a sexually transmitted disease [STD].) Previous outbreaks in Africa appeared to have spread in families by different routes.

“The vaccine was evaluated under the assumption that most or all exposures would be from skin-to-skin contact,” Varma said. MedPage Today. “The head of the penis and the inside of the anus may have characteristics that make them more susceptible to infection, such as a lower dose of virus needed, less abundant antibodies or other components of the immune system, or concurrent STDs at increased risk. It is possible that the level of protection may be the same, but we should not assume it is the same without evaluating it.”

Also, he said, “it is theoretically possible for a monkeypox virus to develop mutations that make it more contagious or virulent to humans. The scientific consensus is that this is less likely to happen as quickly as it does with COVID, given the type of virus. . . COVID is an RNA virus, and monkeypox is a DNA virus.”

Kennedy agreed. “The current outbreak is caused by a strain that has some genetic differences, but is still very close to the strains that caused monkeypox in the 1980s,” he said. “It’s not like COVID-19 where you have a new strain with significant immune evasion every few months. There’s a lot of cross-protection with poxviruses — an immune response to one poxvirus can recognize most other poxviruses. and.”

Correcting a monkeypox prevention message

Despite the weakness of the evidence, the 85% efficacy number is all over the place — sometimes with qualifications, sometimes not. Even Yale University and Harvard University have published health warnings citing the 85% figure without pointing out its uncertainty.

Meanwhile, monkeypox prevention messages aimed at gay and bisexual men continue to vary. Vaccinations are heavily guarded along with other strategies as officials worry about stigmatizing gay men.

Last week, the head of the World Health Organization suggested “reducing the number of your sexual partners, reconsidering sex with new partners and sharing contact details with any new partners to enable follow-up if necessary”.

The CDC offered advice for having sex if someone might be infected: stay 6 feet apart during mutual masturbation and avoid kissing. And magazines save it suggests using condoms, wearing more clothes at parties and bars, and creating sexual “pines” similar to the groups of friends and relatives who socialized only with each other during the COVID-19 pandemic.

Condom suggestions can be especially challenging for men who have sex with men. Many gay men prefer to reduce their risk of HIV transmission by taking preventive drugs such as emtricitabine/tenofovir (Descovy, Truvada) or, if they are HIV positive, by lowering their viral load to undetectable levels through medication.

“The prevention message should be that vaccinations are going to be an essential part of getting this outbreak under control, and we need everyone to be vaccinated as soon as possible,” said Donnelly, the data scientist and advocate for LGBT health. “But even if you’re vaccinated, you’re still at risk, and unprotected anal sex may be the highest risk.”

“Even after vaccination,” he added, “you may want to consider reducing your number of sexual partners and using condoms or following other safer sex approaches.”