United States – According to a new real-world research study, vaccine immunity to mpox deteriorates in the human immune system even in individuals who received the full two-dose course after only a short period of time.
Vaccine Immunity Declines Rapidly
The antibodies dropped down to zero or almost non-detectable values within the first several months of testing, except for a person with a smallpox vaccination history, the scientists said, as reported by HealthDay.
This study found that only a small number (40 percent in total) of unvaccinated men with smallpox had any noticeable antibodies to mpox (Monkeypox) 28 days after the administration of the second dose.
“The results presented here indicate that long-term protective immunity might need a booster dose for its maintenance,” said researcher Dr. Klara Sonden, deputy state epidemiologist for the Public Health Agency of Sweden.
The researcher’s findings state that no clinical trials for the purpose of boost dose for the mpox vaccine are under process and public health guidelines should be informed by such clinical trials.
New monkeypox cases have suddenly begun to increase in 2023, following a decline in the first half of the year in European countries, according to epidemiologists, after a vaccine became available.
A case study also presented at the meeting illustrates the point of the new study: The second case, a 35-year-old man with two doses of Jynneos vaccine, was the result of a breakthrough mpox disease.
In January 2024, and by then two years after getting the vaccine, the man attended a Vienna event with multiple sexual partners that, experts indicated.
After five days, the patient got a fever, chills, headache and painful urination, bloody diarrhea, and itching of the penis and anus. Researchers noted.
Tests turned out the man was suffering from an aggressive and active mpox infection. Finally, after 25 days had passed and a swab test was positive that the infection was cleared, his scabs fell off.
Breakthrough Cases Highlight Risk
“This was Austria’s first monkeypox breakthrough case,” said Dr. Luigi Segagni-Lusignani of the Public Health Authority in Vienna. “Despite no hospitalization, the clinical course was not less severe than in unvaccinated patients, with longer disease duration and higher scores on the monkeypox severity scale.”
In the case of the antibody study, researchers traced these immune responses through a cohort of 100 gay men who had the European mpox vaccine, Vaccinia Ankara–Bavarian Nordic, recently at a sexual health clinic in Stockholm.
Role of Prior Smallpox Vaccination
In particular, the researchers discovered that in the group of men who had been vaccinated against smallpox earlier, only those who still had protective levels of mpox antibodies in their blood were carrying the antibodies at 28 days mark.
Researchers propose that after previous smallpox vaccination, men carried antibodies against smallpox, which enabled them to better adapt to the mpox virus thanks to their memory cells.
“Monkeypox vaccination results in neutralizing antibodies only in a proportion of vaccinees, and a significant decline occurs already during the first-month post-vaccination,” Sonden’s research team concluded.
The researchers specified that the biggest Swedish STD clinic is aiming to conduct a randomized study on booster vaccines. Nevertheless, mpox disease is very rare in Sweden, as reported by HealthDay.
Preliminary Findings Prompt Caution
As the studies were presented at a healthcare forum and not in a peer-reviewed journal, their findings should be regarded as preliminary till final publication.