A new study finds that vaccinating pregnant women for RSV was effective in protecting their newborns from the sickness.

RSV stands for respiratory syncytial virus. It affects the body's breathing system. RSV is most common in babies, but can also affect adults. Most of the time it only causes minor sickness such as runny nose and cough. But in serious cases it can lead to life-threatening disease in some babies and older people.

American drug maker Pfizer did the study. It announced the results Tuesday. The study subjects were given the vaccine in the second half of their pregnancy terms.

The company said its RSV vaccine was nearly 82 percent effective in preventing severe cases of the virus during the first 90 days of a baby's life. At six months of age, the vaccine was found to be 69 percent effective against serious sickness, the study found.

Pfizer said there were no signs of safety problems in mothers or babies.

The company said the study showed the vaccine was most effective against severe disease. For milder sickness, the rate of effectiveness dropped to between 51 to 57 percent.

In the United States, RSV leads to the hospitalization of about 58,000 children younger than age 5 each year. Several hundred children die. About 177,000 adults 65 and older are hospitalized with RSV each year and it kills about 14,000.

Worldwide, about 100,000 children a year die from RSV, most of them in poor countries.

Pfizer said it plans to seek government approval of its RSV vaccine by the end of 2022. If approved, Pfizer's shot could become the first vaccine given to mothers to prevent RSV in young children.

British drug maker GlaxoSmithKline (GSK) is also working on developing a vaccine against RSV.

Both companies recently announced their shots have also shown good results protecting older people.

Kena Swanson is vice president of Pfizer's viral vaccines division. She told Reuters news agency that a vaccine given to mothers "takes advantage of the ability to protect the infant from day one." Swanson added that the results are important because they showed the vaccine is highly effective at protecting babies at "the peak of hospitalization," at around one to two months of age.

Children's hospitals in parts of the U.S. have been reporting worrying levels of RSV cases. While the latest findings will not be able to help that situation, they do raise hopes that one or more vaccines might become available before next fall's RSV season.

"My fingers are crossed," said Dr. William Schaffner, an infectious disease specialist at Vanderbilt University. "We're making inroads," he added.

I'm Bryan Lynn.

The Associated Press and Reuters reported this story. Bryan Lynn adapted the reports for VOA Learning English.

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take advantage of – phr. to use the good things in a situation

peak – n. the highest level or value of something

inroads – n. to start becoming successful at something