Adults whose chronic diseases put them at risk of pneumonia but who are too sick to receive a vaccine may still be protected.
A new study from the University of Calgary’s Cumming School of Medicine has found that vaccinating children against the most common bacterial cause of meningitis and pneumonia is also very effective in preventing disease in unvaccinated adults — a phenomenon commonly referred to as the "herd effect."
The benefit in adults appears to be similar for both healthy adults and those with underlying chronic illnesses. The study was published in Clinical Infectious Diseases in April.
Looking at routine vaccine in Alberta's childhood immunization program
The pneumococcal conjugate vaccine provides immunity against infection from Streptococcus pneumoniae, the bacteria that cause pneumonia and other diseases such as meningitis. It is a routine vaccine in Alberta’s childhood immunization program and was originally introduced into the program in 2002 to protect against seven strains of the disease-causing bacteria. A newer vaccine, protecting against 13 strains of the bacteria, was introduced into the program in 2010.
“It’s well known that there should be benefits to those beyond those who are vaccinated,” says Dr. Jason Cabaj, lead author on the study, clinical assistant professor at the university’s Department of Community Health Sciences and member of the university’s O’Brien Institute for Public Health.
“The vaccine eliminates the ability of the bacteria to colonize in people’s noses and throats, so they aren’t spreading the bacteria around.”
Overall pneumonia rates decreased in both children and adults after vaccine
Adults with chronic or life-threatening conditions are more likely to develop pneumonia or other invasive infections. These individuals are often more likely to develop potentially fatal complications and are also often ineligible to receive the vaccine.
Researchers evaluated the incidence of invasive pneumococcal disease (IPD) in Calgary over a 13-year time frame, both before the vaccine was introduced into the childhood vaccination programs, and after introduction.
They found that overall IPD rates (in children and adults combined) decreased by 37 per cent after the initial implementation of the vaccine.
Vaccinating children for this bacteria can prevent diseases in adults
“Young children are the main reservoir for this bacteria so they can routinely pass it on to other individuals,” says study co-author Dr. Jim Kellner, head of the university’s Department of Paediatrics and member of the university’s Alberta Children’s Hospital Research Institute.
“That’s why vaccinating children works so well in preventing disease in adults, although adults still do not acquire the same level of protection.”
Researchers will continue to monitor the effect this program change may have on the spread of the disease within the community.