A vaccine candidate developed to protect vulnerable older adults against a common viral illness has shown 80% efficacy in reducing the odds of developing dangerous lower respiratory tract diseases, developer Johnson & Johnson announced Saturday.

The shot targets respiratory syncytial virus (RSV), a very common bug that is one of the top causes of bronchitis and pneumonia and can be deadly in seniors. In a mid-stage study, the vaccine protected participants aged 65 years and older against these and other lower respiratory tract diseases, J&J reported.

The RSV vaccine also was found to be 70% protective against any symptomatic RSV-associated acute respiratory infection, the company said in a statement.

Investigators followed more than 5,700 participants across 40 U.S. sites throughout a single RSV season. The shot was “generally well tolerated” by all vaccinated study participants, they reported. Participants who were tested for immunity markers showed a substantial increase in RSV neutralizing antibodies 14 days after being vaccinated, J&J said. 

The drugmaker now is launching a late-stage (phase 3) study to evaluate efficacy, safety and immunogenicity of the vaccine against lower respiratory tract disease caused by RSV when compared with placebo in approximately 23,000 older adults throughout North America and internationally.

It is estimated that more than 177,000 older adults are hospitalized and 14,000 of them die in the United States due to RSV infection, according to the Centers for Disease Control and Prevention.

Pfizer also has started a phase 3 trial of its own RSV vaccine.

The current study results were presented at the virtual IDWeek 2021 conference on Saturday, Oct. 2.