Johnson & Johnson coronavirus vaccine generates immune response, few side effects, in early trials - CNN

"A single dose of Ad26.COV2.S elicited a strong humoral response in a majority of vaccine recipients, with the presence of S-binding and neutralizing antibodies in more than 90% of participants, regardless of either age group or vaccine dose," the researchers wrote.

"An efficacious single-dose Covid-19 vaccine have obvious logistic advantages over a two-dose vaccine, especially during a pandemic." The company is studying whether a second dose increases efficacy or durability of the immune response.

Side effects included headache, body ache and, more rarely, fever.

"The Company anticipates announcing topline Phase 3 data for its single-dose Janssen COVID-19 vaccine candidate in late January 2021; however, as this trial is dependent on disease events, the timing is approximate," Johnson & Johnson said in a statement.

But with the pandemic raging in the US and Europe, vaccine experts say, answers are coming quickly for vaccine trials.

"If the single-dose vaccine is shown to be safe and effective, the Company expects to submit an application for Emergency Use Authorization with the U.S.

Food and Drug Administration shortly afterwards, with other regulatory applications around the world to be made subsequently," Johnson & Johnson added.

All of the companies making coronavirus vaccine have been manufacturing doses even as they test them, so they can roll them straight out to people should they get FDA authorization.