Monkeypox vaccine study raises questions about protection, shows research

The recommended series of shots with Bavarian Nordic A/S's Jynneos vaccine yielded relatively low levels of monkeypox antibodies with poor neutralizing capacity, researchers said

The monkeypox vaccine that’s become the main method doctors are using to try to stop the global scourge may be less potent than hoped, new research shows.   

The recommended series of shots with Bavarian Nordic A/S’s Jynneos vaccine yielded relatively low levels of monkeypox antibodies with poor neutralizing capacity, researchers at the Erasmus University Medical Center in Rotterdam, Netherlands, said. Those immunized hadn’t been previously infected or vaccinated against smallpox, which is believed to provide some protection against monkeypox. 

Neutralizing antibodies have become part of the common lexicon during the Covid era thanks to their ability to bind to the coronavirus and stop it from entering healthy cells. Although these proteins are almost certainly needed to prevent a monkeypox infection and the rash it causes, scientists don’t know yet what levels are required to confer protection.

“The level of optimism for the vaccine far exceeds the data currently available,” said Helen Petousis-Harris, a vaccinologist at the University of Auckland, who wasn’t involved in the research. “There are a lot of information gaps and we have to be cautious as it gets rolled out, especially to avoid vaccinated people having a false sense of security.”

Protection Question

The finding of lower-than-expected levels of neutralizing antibodies raises questions about how well vaccinated individuals are protected, wrote Erasmus scientists Marion Koopmans, Rory de Vries and their co-authors in the paper that was released Thursday ahead of peer review. 

“Studies following vaccinated individuals are necessary to further assess vaccine efficacy,” they said. 

Representatives for Bavarian Nordic didn’t immediately respond to requests for comment made after hours.

Authorities in more than 70 countries are seeking supplies of the Danish company’s vaccine, also sold as Imvamune in Canada and Imvanex in Europe, to thwart the global spread of monkeypox. It has infected more than 50,000 people since a flareup of the disease was reported in the UK in early May. 

While some scientists are testing dose-sparing approaches to stretch limited supplies of the immunization, the Erasmus work found dose sparing “has a negative effect” on vaccination. A third dose boosts the antibody response, as does immunizing individuals who were vaccinated against smallpox decades earlier, they found.

Monkeypox is closely related to variola, the virus which causes smallpox -- the first human disease to be eradicated. The Bavarian Nordic vaccine is deemed a safer immunization than the one that wiped out smallpox as it uses a weakened, non-replicating version of a related virus. 

Efficacy data on its use against monkeypox in humans is lacking, the Erasmus scientists said. Experiments in animals showed it generated both antibodies and T-cells against monkeypox, but not enough to prevent infection or the emergence of some skin lesions.