Steven A. Rubin, PhD, works with a flask of cells inoculated with mumps virus in the FDA’s laboratories in Silver Spring, Md. Courtesy of FDA
In a light-filled lab at the Food and Drug Administration (FDA), a collection of small containers are growing the bacteria that cause whooping cough.
In a nearby lab, cultures of the mumps virus also are being grown for studies aimed at improving the effectiveness of the mumps vaccine. This work is being done because reported cases of mumps and whooping cough (also called “pertussis”) have risen in recent years, even though many people are vaccinated.
As part of the FDA’s commitment to protect the public health, researchers are seeking to better understand why these outbreaks occur. They’re working to figure out how to make current U.S. vaccines—which are already safe and effective—even better. And they’re reminding consumers that vaccination is still the best protection from these diseases and their potentially serious complications.
A vaccine is a medical product that stimulates a person’s immune system to protect against a specific disease. The FDA assures the safety and effectiveness of vaccines for use in the United States, and only approves vaccines that it has determined to be safe and effective.
“Vaccines protect against serious diseases and save lives,” notes Steven A. Rubin, PhD, chief of the Laboratory of Method Development at the FDA’s Center for Biologics Evaluation and Research.
Rubin is studying immune responses to the vaccine used to prevent mumps, a contagious disease caused by a virus. Common symptoms include a swollen jaw and puffy cheeks—both due to painful swelling of the salivary glands—along with severe headache.
Although it rarely results in death, mumps can be serious. Before vaccines were developed, mumps was the leading cause of viral encephalitis (inflammation of the brain) and sudden onset deafness in the United States.
Since the U.S. mumps vaccine program started in 1967, there has been a more than 99 percent decrease in the nation’s reported mumps cases. “Mumps is no longer common in the United States, but sporadic outbreaks still occur, even in highly vaccinated populations,” Rubin says. “Mumps was historically a disease of childhood, but outbreaks now typically involve young adults, particularly in high density, close contact environments such as on college and university campuses.”
Today in the United States, children get two doses of a combination vaccine that contains a mumps component. “But our research indicates that by college age, levels of anti-mumps virus antibodies had declined substantially,” Rubin adds, which might leave people unprotected.
So, in collaboration with the Centers for Disease Control and Prevention (CDC), Rubin and his team studied college-age participants’ response to a third vaccine dose. Participants responded with a sharp increase in antibodies within the first month after vaccination, but levels went down to nearly pre-dose levels within one year.
“This suggests that an additional dose of vaccine is unlikely to provide a long-term solution,” Rubin says. “We are now looking into other ways of improving the vaccine, such as optimizing the structure of the vaccine virus to trigger the production of longer-lasting, more robust antibodies.”
Tod J. Merkel, PhD, evaluates a plate of pertussis colonies in the FDA’s laboratories in Silver Spring, Md. Photo courtesy of FDA
The FDA is studying whooping cough because rates have been rising steadily over the last 20 years. Also called pertussis, this serious and contagious disease is caused by a bacterium. It can cause violent and rapid coughing that continues until the air is gone from the lungs and a person inhales with a loud “whooping” sound.
“Pertussis is most severe and can be extremely dangerous in young infants, especially those who are too young to have completed the infant vaccination series against pertussis,” says researcher Tod J. Merkel, PhD, principal investigator at the FDA’s Laboratory of Respiratory and Special Pathogens. “Whooping cough can cause serious and sometimes life-threatening complications, permanent disability, and even death, especially in infants and young children.”
U.S. vaccines for this disease have a long history. The first “whole-cell” vaccines to protect against diphtheria, tetanus, and pertussis became available in the United States in the 1940s and contained killed, but “whole,” Bordetella pertussis bacteria. Concerns about side effects of these earlier vaccines led to the development of DTaP vaccines; the “a” stands for “acellular,” indicating that these vaccines contain only parts of the pertussis bacteria instead of killed whole cells. Acellular pertussis vaccines result in fewer side effects. The FDA first approved a DTaP vaccine in 1996 for use in infants as young as 6 weeks.
Today, Merkel is studying the pertussis vaccine in baboons, an animal model that closely reproduces the way whooping cough affects people.
His findings suggest that although people immunized with acellular vaccines may be protected from whooping cough symptoms (sometimes referred to as being “asymptomatic”), they may still become infected. And these people can then infect others, including infants.
“That was an important finding. It provided a path forward,” Merkel explains. “Now our work is focused on trying to understand the ways we can improve the vaccine so it prevents infection and transmission, in addition to preventing disease symptoms.”
It is clearly better to be vaccinated than not vaccinated, both Rubin and Merkel say.
“Two doses of the mumps vaccine used in the United States vaccine are about 88 percent effective, which is very good. No vaccine is 100 percent effective,” Rubin explains. “And if a vaccinated person does get mumps—an uncommon event—symptoms will be more mild and last a shorter time, compared to symptoms in someone not vaccinated.”
That fact about symptoms is also true for the whooping cough vaccine. “People who are vaccinated are less likely to get sick, and vaccinated individuals who do get sick experience a more mild illness,” Merkel explains. “Vaccinated individuals are protected from severe disease.”
“If you’re an adult and haven’t received your whooping cough vaccine in the last 10 years, you should,” Merkel continues. “Vaccination is especially important if you’re pregnant because your antibodies can be passed to your fetus, providing your newborn with critical protection during the first months of life.”
Talk to your healthcare provider if you have questions or concerns about mumps, whooping cough, or their vaccines.
And know that FDA studies will continue. “We enjoy the science,” says Merkel. “But what’s driving our research is the desire to make a difference.”