As concerns grow over a large outbreak of a particularly virulent form of mpox in central Africa and a slight increase in cases in the United States since early last year, the mpox vaccine appears to offer long-term protection, the Centers for Disease Control and Prevention reported Thursday.
In a separate report, the CDC said overall new mpox infections in the United States remained at a low and stable level — about 60 cases per week, compared with 3,000 cases per week at the peak of the outbreak in summer 2022 – over the last few months. However, so far this year, cases are high nationally compared to the same period in 2023 and have seen a sharp increase in New York.
People who have received two doses of the Jynneos mpox vaccine are protected from infection and do not need a booster at this time, according to the CDC.
Public health experts fear that the launch of the summer travel season and upcoming LGBTQ pride festivals in cities across the country will lead to greater sexual connectivity among gay and bisexual men and potentially accelerate transmission of the virus. mpox.
Christina Hutson, chief of the CDC’s Poxvirus and Rabies Branch, and other public health experts told NBC News that now is not the time to become complacent about mpox (formerly called monkeypox). . The various factors that have likely kept the U.S. outbreak relatively under control since late 2022—including vaccination, infection-induced immunity, and change in sexual behavior—may be tenuous.
The mpox epidemic is “on the verge of returning to normal,” said Dr. Jeffrey Klausner, an infectious disease expert at the University of Southern California. Infections quickly spread around the world starting in May 2022 and made that summer a misery for many gay and bisexual men before crashing worldwide.
Importantly, the proportion of at-risk American gay and bisexual men fully vaccinated against mpox is considered insufficient to provide long-term protection to this vulnerable population.
“Vaccination is an essential way to protect yourself and others,” Hutson said. “It is important that people at risk of exposure to mpox who have not yet recovered from mpox – including some gay, bisexual men and other men who have sex with men – complete the Jynneos vaccination series at two doses.”
On May 16, the CDC released a disturbing report on nearly 20,000 recent cases of what is called mpox clade 1 that have been documented in the Democratic Republic of Congo, or DRC, since January 2023.
Of concern, this viral clade appears to be more transmissible and cause higher rates of severe illness and death compared to mpox clade 2, which caused the recent global outbreak. Five percent of people diagnosed with clade 1 in the DRC have died, compared to just 0.2% of the 96,000 people affected by the global clade 2 outbreak.
To date, no cases of clade 1 have been reported outside of the handful of African countries where mpox has been endemic for decades. In December, the CDC first alerted health care providers to the possibility that this more harmful viral clade could hit the United States.
“We’re facing a serious and potentially dangerous situation,” Ira Longini, a biostatistician at the University of Florida, said of clade 1’s potential for global spread. “But we really don’t know.”
Dr. Boghuma Titanji, an assistant professor at Emory University School of Medicine, suggested that the Jynneos vaccine would likely provide protection against clade 1. The Jynneos vaccine is approved in the United States for mpox, regardless of the clade.
“It is reasonable to expect that there will be some immune cross-protection,” she said of immunity from both the vaccine and previous clade 2 infection. .
A clinical trial of the Jynneos vaccine is underway among health workers in the DRC. It is not expected to be completed until the end of next year.
But the vaccine was not otherwise deployed in the DRC, a missed opportunity to help control the outbreak in the country and prevent the spread of clade 1 globally, Titanji said.
Dr Placide Mbala, head of epidemiology and global health at the University of Kinshasa in the DRC, said the country had seen “a lot of interest” from world public health leaders in provision of such assistance.
“But we are still waiting for concrete measures,” Mbala said.
During the clade 2 epidemic, mpox was massively transmitted via oral and anal sex between men. Transgender people have also been disproportionately affected. The virus has not been transmitted easily through air or surfaces, in health care settings, or through casual, non-sexual contact.
In an interview earlier this year, Dr. Jennifer McQuiston, an epidemiologist at the CDC, said that mpox “should be considered an STD.” The good news is that it is a preventable STD.
Several studies of real-world use of the Jynneos vaccine have suggested that receiving both doses is associated with a 66-89% lower infection rate and that one dose is 36-75% effective.
In one of the new CDC reports, agency investigators analyzed demographics and clinical characteristics regarding 271 cases of mpox from the start of the outbreak in the United States in May 2022 through May 2024 among fully vaccinated people in 27 US jurisdictions who provided sufficient related data.
According to a CDC official, the agency estimates that only 0.1% of the fully vaccinated population developed a breakthrough infection. These reported cases represented 0.8% of all 32,819 mpox diagnoses nationwide. Thirteen percent of mpox cases involved partially vaccinated people.
The CDC estimates that 2 million men in the United States are at significant risk of mpox because they have sex with multiple male partners or because they are HIV positive; HIV-positive people had a high mpox diagnosis rate. Among the overall group of at-risk gay and bisexual men, only about 25% have been fully vaccinated and another 14% have received a Jynneos shot.
Consistent with previous studies, the new CDC report found that full vaccination was associated with less severe illness and a lower hospitalization rate.
The 56 deaths from mpox involved unvaccinated people.
Recent research has raised concerns that the antibodies caused by Jynneos may wane over time. But CDC investigators have found evidence that, at least so far, the vaccine’s actual protection against infection has not diminished, perhaps due to so-called innate immunity or cellular.
Shortly after the vaccine’s first rollout, in mid-summer 2022, U.S. health officials began to alleviate the temporary shortage by changing its administration from a traditional subcutaneous (under the skin) injection to one intradermal injection (into the skin) which allowed a much lower dose. dose.
The new CDC report found no evidence that this change in vaccine application compromised vaccine effectiveness.
A separate new CDC analysis of recent mpox diagnoses in the United States found that the virus is still overwhelmingly seen in gay and bisexual men. Only 0.4% of recent cases involved people under the age of 18.
Between October and April, 1,802 probable and confirmed cases of mpox were reported to the CDC by 42 jurisdictions – for an average weekly rate, which has remained essentially stable, of 59 cases. In contrast, the country recorded between 2,000 and 3,300 weekly cases at the peak of the epidemic between mid-July and the end of August 2022.
And yet, CDC records show that the nearly 750 cases of mpox seen this year through mid-April are more than double the figure reported during the comparable period in 2023. New York City has seen the case rates almost quintuple between these two. periods, with 191 cases so far in 2024.
As for concerns about how a clade 1 outbreak might occur in the United States, infectious disease experts said they can only speculate about whether better health care, through example, could result in a lower mortality rate than in the DRC. Deaths from clade 2 globally have occurred largely in people with weakened immune systems, primarily due to untreated HIV.
Other unknowns include how and among which groups clade 1 might tend to transmit in Western countries. The outbreak in the DRC occurred both among men with multiple male sexual partners and among female sex workers and their contacts. And two thirds of clade 1 epidemics in the DRC concern people under the age of 16; only slightly more than 1% of the global clade 2 outbreak involved minors.
Epidemiologists are seeing evidence of sustained person-to-person transmission in one DRC province, where cases are mostly among adults.
Although this transmission apparently occurs largely sexually, compared to mpox clade 1 clade 2, it shows signs that it can nevertheless be transmitted more easily in the absence of sexual contact. However, clade 1 still appears to require close personal contact and non-sexual transmission appears largely limited to household settings. In addition, significant transmission among children could be due in part, according to the recent CDC report, to multiple spillovers from wild animals encountered by young people in rural areas.
CDC officials believe that widespread transmission of clade 1 among children in the United States is much less likely, due to the lack of animal reservoir, less crowded living quarters, and better cleaning and monitoring. better hygiene.
Emory’s Titanji raised concerns that the gay and bisexual men in her care quickly lost interest in mpox vaccination after the outbreak ceased to be a major concern for them. During the fall of 2022, the rate of weekly distribution of Jynneos injections in the country fell alongside the rate of mpox cases.
Since then, no substantial progress has been made in increasing the proportion of at-risk gay and bisexual men who have received both doses of Jynneos.
“If you are not yet vaccinated and you meet the criteria, go get vaccinated,” Titanji said. “We cannot rest on our laurels about the response moving forward.”
News Source : www.nbcnews.com
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