Late last week a notable group of Dutch researchers published a preprint study on the neutralizing antibodies produced by two subcutaneous doses of Bavarian Nordic's monkeypox vaccine, Jynneos (MVA), and it indicated the dose-sparing strategy might not yield a very strong immune response.

"The primary MVA immunization series in non-primed individuals yielded relatively low levels of neutralizing antibodies, raising the question whether vaccinated individuals are now protected, and what the correlates of protection against MPXV [monkeypox virus] infection are," they wrote. "At this moment it is unclear what the relatively low MPXV neutralizing titers mean for protection against disease and transmissibility."

Subcutaneous, or intradermal, dosing is being employed in the United States as a way of using one-fifth the usual vaccine dose, thereby allowing many more people to get vaccinated using the same vaccine supply. Officials hoped the strategy would provide the same level of protection as a full Jynneos dose.

But the new study shows low levels of antibody response after both one and two doses of subcutaneous vaccine.