As officials warn about possible summer rise in mpox, new studies show two doses of vaccine are better than one

The studies found that two doses of the Jynneos mpox vaccine are 97 percent effective at preventing mpox, while one dose is only 66 percent effective.

As officials warn about possible summer rise in mpox, new studies show two doses of vaccine are better than one


Three new studies have shown that Jynneos' mpox vaccine is more effective when given in two doses than if it were administered only once.

In a Thursday telebriefing, Dr. Christopher Braden of the US Centers for Disease Control and Prevention's mpox response, incident manager, stated that 'vaccine effectiveness estimates ranged from 36 to 75 percent for a single dose and from 66% to 86 percent for two doses'.

He said that 'what we take from these three study is that the vaccination effectiveness is substantial, and that two doses are definitely better than one'. It will prevent people from contracting mpox, and will also help them avoid serious disease or death.

The studies are in response to an outbreak of monkeypox (formerly known as mpox) that spread in multiple countries in 2017. This resulted in over 30,000 cases across the United States. These cases disproportionately affected gay and bisexual males.

The US Food and Drug Administration approved an emergency use authorization in August for the Jynneos MPox two-dose vaccine that is to be administered to adults at high risk. The vaccine is usually administered in two doses four weeks apart. However, during the outbreak last year, single doses of the vaccine were given to spread out supply and ensure that as many people could be inoculated.

The number of mpox outbreaks in the United States have decreased significantly since August's peak. However, the CDC is now urging those who still haven't completed the second dose of Jynneos to do so before this summer.

According to the CDC only 23% have received a full vaccination in America.

Effectiveness of the mpox vaccine

A real-world study conducted in 12 US jurisdictions between August 2022 and March 2023 suggests that Jynneos MPox vaccine is 85.9% effective for preventing symptoms of mpox infection, while the vaccine's effectiveness after a single dose is 75.2%.

Researchers from the CDC and US institutions analyzed 309 mpox patients and 608 controls to determine the effectiveness of the vaccine against mpox in men who have sex only with men or transgender adults aged 18-49.

The results of this study are consistent and similar to those obtained in previous studies evaluating the effectiveness or performance of vaccines,' wrote the researchers in their report published in Thursday's Morbidity and Mortality Weekly Report by the CDC.

It is still unknown how long protection will last from a vaccine over time. Researchers from the CDC, as well as other US institutions, stated that due to this unknown, those at a higher risk of mpox are advised to complete the two-dose vaccine series.

A study published in the CDC’s Morbidity and Mortality Weekly Report on Thursday suggests that two doses of Jynneos are more effective than one dose against symptomatic mpox infection.

Researchers at the New York State Department of Health, as well as other institutions, collected data between June and December of last, when 375 cases of mpox were reported to the department. More than 27,000 doses of vaccination were also recorded.

Researchers compared the results of their analysis with those of 255 patients diagnosed with primary syphilis or rectal gonorrhea in New York.

The analysis shows that when data from both the one-dose and two-dose vaccines are combined, 75.7% of its overall effectiveness is achieved.

Researchers wrote that the mpox epidemic 'rapidly decreased during summer 2022 following extensive public health and vaccine efforts and individual behavioral changes'. However, how much of the decline can be attributed to the effectiveness of the vaccine versus the behavior change or seasonal variations in the spread pattern remains unknown.

Researchers wrote that 'Global mpox spreading continues and could accelerate during summer 2023 due to remaining unvaccinated people with behavioral risk'. They added that their findings supported the recommendation of two doses as the best protection.

In the United States, a separate study published in the New England Journal of Medicine on Thursday suggests that the Jynneos vaccination was 66% effective against the mpox virus after two doses, and 35.8% effective after just one dose. Only people with no immunocompromising conditions were able to achieve 76.3% vaccine effectiveness after two doses and only 40.8% after one.

Researchers from the CDC and Epic Research, a subsidiary of Epic Health Care Software, analyzed the data of more than 2,000 mpox patients and over 8,000 controls who had no history of mpox, but were at similar risk for both diseases. Researchers found that 25 patients with mpox had received two doses Jynneos, compared to 335 patients with control. The study was conducted from August to Novembre of last year.

Braden stated that the NEJM study was a good study, and it is important to conduct multiple studies in order to determine the true effectiveness of vaccines in the population.

The data from Epic's Cosmos Database showed that people with mpox had a lower likelihood of being vaccinated compared to the control patients.

Jackie Gerhart said that two of every three cases of mpox are prevented in people who receive two doses. One dose is enough to prevent one of every three cases of mpox, according to an email from Jackie Gerhart. She is the chief medical officer of Epic Research, a family physician.

'Vaccination is still the best way to prevent illness. Although there have been reports of breakthrough cases of mpox in vaccinated people, it's still recommended to get vaccinated. In the future we hope to study waning cases and breakthrough cases,' Gerhart wrote in an email.

Mpox is spread by skin-to-skin contacts. She said that the mpox epidemic last year began in spring/summer, possibly due to festivals, pride celebrations and other summer events. Public health officials, community advocates, and clinicians have spread the word about mpox. We know more than we did last year. We also have a vaccine that is available more easily this year. We are more prepared to help and support those at risk through prevention measures and vaccination.

It's not the first time that CDC researchers have shown that two doses Jynneos offer more protection against mpox compared to just one dose.

The CDC published a separate study in December that found that the number of mpox infections among US men aged 18 to 49 was 9,6 times higher among those who hadn't been vaccinated than among those who had two doses and 7,4 times higher among those who only had the first dose.

The previous study showed that for every mpox infection among those who had received two doses of the vaccine, there were ten among non-vaccinated people.

The vaccination level is not what we need.

As summer approaches, health officials at the federal, state, and local levels continue to work on raising awareness about the importance of mpox vaccine for those most at risk.

In an October study, the CDC reported that only 57.6% of nearly 500,000 Jynneos recipients who were eligible for a subsequent dose received it.

The symptoms of those who have been vaccinated appear milder, but the National Association of County and City Health Officials' chief executive officer Lori Tremmel Freeman told CNN this week.

She said that there was much more to be unpacked, but the vaccine is still the best way to avoid severe diseases, such as hospitalization or death. People should get vaccinated at least two weeks before attending major events with a risk of exposure to the mpox virus.

Mpox, a virus, spreads by close contact. While it can affect anyone, the majority of cases were among men who had sex with other men during last year's epidemic. Mpox is a viral disease that spreads through close contact. While it can infect anyone, during last year's outbreak, infections were mostly among men who had sex with other men. Rarely, mpox is fatal, especially in people with weak immune systems.

In a Thursday telebriefing, Dr. Demetre daskalakis, White House deputy coordinator for the national mpox outbreak response, stated that vaccination can make getting and spreading the mpox more difficult. It may also reduce the risk of serious illness, hospitalization, and death.

Without renewed prevention efforts, particularly vaccination, we're definitely at risk, and in fact, a substantial chance of a resurgence. Daskalakis added that this is particularly concerning as summer approaches. The CDC is already planning to work with LGBTQ Pride Month event organizers in June to increase awareness about the importance of vaccines.

According to CDC estimates, there are approximately 1.7 million people who could benefit by vaccine.

The CDC issued a Health Alert Network update on Monday, warning of the risk for new mpox infections this spring and summer. It also described a rise in cases already detected in the Chicago region.

Daskalakis reported Thursday that a total 21 people had been diagnosed as having mpox in the Chicago cluster. He said that the majority of cases are gay or bisexual males, and they have mild symptoms. No hospitalizations were reported.

The agency stated that the spring and summer seasons in 2023 may see a resurgence as people gather at festivals and other events. The Health Alert Network's (HAN) Health Update aims to inform public health agencies and clinicians about the possibility of new outbreaks or clusters of mpox and provide resources for clinical evaluation, vaccination and testing.