JnJ vaccine raises neutralizing antibodies, prevents severe COVID-19 in hamsters

"However, nonhuman primates typically don't get the severe clinical disease, and thus it was important to study whether this vaccine could prevent severe pneumonia and death due to SARS-CoV-2 in hamsters, which are more susceptible to clinical disease," Barouch said.

The scientists developed a series of vaccine candidates designed to express different variants of the SARS-CoV-2 spike protein, which is the major target for neutralizing antibodies.

In the current study, they immunized Syrian golden hamsters with a single injection of the Ad26-based SARS-CoV-2 vaccine, which induced neutralising antibodies in all the test animals.

Four weeks later, when the hamsters were exposed to a high dose of SARS-CoV-2, the study found that vaccinated animals lost less weight, had less virus in their lungs and other organs, and also demonstrated lower mortality than unvaccinated control animals.

The scientists also found that neutralizing antibody responses were inversely correlated with weight loss and viral loads in respiratory tissues.

They said the vaccine is currently being evaluated in clinical studies to establish the performance of the vaccine candidate in humans.

"This hamster model of severe COVID-19 disease should prove useful to complement current nonhuman primate models in the evaluation of candidate vaccines and therapeutics," Barouch said.

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