Questions are being raised over the effectiveness of the third-generation monkeypox vaccine used in Australia after a study found immunisation induced only low levels of neutralising antibodies.

The Dutch research, which has not been peer reviewed, found people receiving one dose of the Jynneos vaccinia vaccine “hardly developed” antibody responses and that the second dose was required to achieve detectable levels.

Even then, those antibodies had  low neutralising capacity unless the individual had previously been exposed to monkeypox or to a previous smallpox vaccination.

“At this moment, it is unclear what the relatively low [monkeypox vaccine] neutralising titres mean for protection against disease and transmissibility,” wrote the authors, from Erasmus University Medical Centre in Rotterdam, the Netherlands.