The world’s second deadliest childhood infection could finally meet its match as two potential vaccines pass through clinical trials.

Of all the vaccines to prevent infections, one has yet to come out to stop the respiratory syncytial virus (RSV).

But recent developments show this common infection, which can be deadly in infants and the elderly, may soon meet its match.

The latest discovery comes from a research team from the Pirbright Institute in the United Kingdom. The results were published in the journal Science Translational Medicine.

Dr. Geraldine Taylor, a vaccinology researcher at Pirbright and lead researcher of the new study, told Healthline a novel method using two modified viruses triggered a strong immune response against the RSV virus.

One of the modified viruses, PanAd3-RSV, was developed from a chimpanzee adenovirus. Taylor says vaccines based off this kind of adenovirus have been shown to be safe in a number of clinical trials.

“The chimpanzee adenoviruses are closely related to human adenoviruses, as one might expect from closely related human and chimpanzee hosts,” Taylor said.

The research teams tested their vaccines in young calves — mimicking conditions in young human children — and in a phase I trial in 42 healthy adults.

Both tests showed using a one-two punch primed the animals’ and adults’ immune systems against the virus with only mild side effects.

Taylor says the two new studies support further clinical development of this vaccine.

“Our findings in young calves suggest that the virus-vectored vaccine approach would be tolerated by healthy individuals, infants, and the elderly,” she said. “However, careful surveillance of the safety and immunogenicity of the vaccine will need to be carried out as it progresses through clinical development toward the target populations.”

Get the Facts on Your Respiratory System »

RSV is the most common cause of bronchitis and pneumonia in children less than a year old and the second killer of infants from 1 month to 1 year old. The first is malaria.

Most healthy people with RSV only experience mild symptoms and recover in about a week.

However, infants, the elderly, and people with compromised immune systems can develop potentially deadly infections.

Each year, more than 57,000 children under the age of 5 are hospitalized for RSV infections.

About 177,000 seniors are hospitalized and 14,000 die from RSV, according to the U.S. Centers for Disease Control and Prevention.

“The development of a safe and effective RSV vaccine will therefore have a significant impact on global health,” Taylor said.

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An effective vaccine for RSV hasn’t come to market yet, as safety has been an issue in testing in children.

This week vaccine company Novavax announced results from a phase II clinical trial for a potential vaccine against RSV.

Their test involved 1,600 adults age 60 and over and showed it could lessen symptoms and infection rates in people more vulnerable to RSV.

The three trials reduced cases of bronchitis and pneumonia by 40 to 60 percent. A 60 percent efficacy rate would mean 18 million young children worldwide a year would not get those diseases.

Stanley C. Erck, Novavax president and CEO, called the findings “groundbreaking” and expects the next phase of testing to begin later this year.

“The development of an RSV vaccine has been a decades-long challenge,” he said in a press release.

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Vaccines work in a community setting by having 97 percent of the population vaccinated.

This prevents the spread of the disease to people too young or too sick to receive vaccinations. This is known as herd immunity.

The vaccine Taylor and other researchers are working on is under evaluation in healthy older adults aged 60 to 75 years. It’s expected to enter a pediatric development program later this year.

“Virus-vectored vaccines such as those described in our paper are well-tolerated and safe in (healthy adults) and could be used in vulnerable individuals,” she said.

Taylor says whether their vaccine could induce herd immunity is unclear and dependent on the level of protection the vaccine would afford and how long it works.

Natural immunity to RSV, she said, isn’t lifelong and a person can be infected more than once.

But, virus-vectored vaccines such as theirs can be used in people more vulnerable to infection and in people around them, she said.

“Nevertheless, vaccination of close contacts of people particularly vulnerable to RSV infection could help to prevent virus transmission,” Taylor said. “Similarly, an RSV vaccine to boost immunity in hospital staff could help to reduce the spread of RSV in pediatric wards during the winter months.”