One shot is good. Two are even better when seeking protection against mpox. That is the conclusion of a new so-called real-world study in the US of Bavarian Nordic’s mpox vaccine, which is marketed under the name Jynneos, also called Imvanex and Imvamune, disclosed by the national public health agency, US Centers for Disease Control and Prevention (CDC). 

The study shows that Bavarian Nordic’s vaccine, when given in two doses, is estimated to be 85.9% effective against mpox, while protection at a single dose was found to be 75.2% effective in the study involving 900 subjects.

The announcement comes as early signs point to a potential resurgence of mpox cases in the US this summer, and the CDC has initiated a preventive strategy by which at-risk people are offered the vaccine. 

The advice is that people in the risk group get two doses. 

“This is indicative of these vaccines working and that our strategy of vaccinating people with two doses really remains core to our efforts to prevent mpox,” said Demetre Daskalakis, deputy coordinator of the White House National Mpox Response, according to pharma industry media Fiercepharma.

However, another CDC real-world study conducted in a larger pool of individuals showed much lower efficacy for Jynneos, according to results published Thursday in The New England Journal of Medicine, Fiercepharma writes. 

In a case-control analysis of more than 10,000 people from a nationwide electronic health record database, Jynneos was estimated to be 66% effective after two doses, whereas the one-dose efficacy was just 35.8%.

A lucrative business

Despite their differences, both studies showed that one vaccine dose was good and that two doses were better, Daskalakis recently asserted. He also emphasized that the efficacy data only pertains to the prevention of symptomatic infection and doesn’t entail other benefits like reducing disease severity.

Bavarian Nordic’s smallpox/mpox vaccine rose in prominence last year when an outbreak of mpox propelled demand and increased the Danish vaccine maker’s order book.

In the first quarter of 2023, sales of the vaccine amounted to DKK 848m (USD 123.1m) – in the same quarter the year before, the product didn’t generate any sales at all. After its approval in the US in 2019, Bavarian Nordic has upgraded its guidance no less than seven times, citing demand for the vaccine.

The mpox outbreak has since quieted down but is now again on the rise in some areas of the US. Bavarian Nordic has already secured a few small orders this year, CEO Paul Chaplin told Danish business daily Børsen in May.

”We are negotiating some slightly bigger orders. Should they materialize, we might [upgrade],” Chaplin said.