Daily contact with young children increases the risk of acquiring pneumonia-causing bacteria in elderly adults, a recent study has revealed.

Streptococcus pneumonia or pneumococcus is a bacteria associated with ear and sinus infections and severe diseases such as pneumonia, sepsis, and meningitis. Around two million deaths worldwide every year are associated with pneumococcal infections, primarily affecting children below the age of two and the elderly.

Pneumococcal pneumonia leads to over 150,000 hospitalizations in the USA every year. It is the primary bacterial cause of childhood pneumonia, particularly in children under 5 years old. Among adults, pneumococci contribute to 10% to 30% of cases of community-acquired pneumonia.

Pneumococci bacteria typically live in the respiratory tract of healthy persons which then gets transmitted via respiratory droplets. According to the CDC estimates, around 20% to 60 % of school-age children may be colonized, while only 5% to 10% of adults without children are colonized.

According to the findings of the latest study that will be presented at this year's European Congress of Clinical Microbiology and Infectious Diseases (ECCMID 2024) in Barcelona, Spain, adults over the age of 60 who have daily contact with children have six times more risk of being colonized with pneumonia-causing bacteria than those without any contact with children.

To understand the pneumococcal transmission among adults aged 60 and older and the risks of acquiring pneumococcus in the community, researchers conducted a long-term study in New Haven, Connecticut. The participants were elderly adults without young children living in the household.

A total of 183 adults with an average age of 70 from 93 households were enrolled in the study. Researchers collected saliva samples and questionnaire data on social behaviors and health every two weeks across six visits for 10 weeks.

"The analyses found that overall, 52/1,088 (4.8%) samples tested positive for pneumococcus, with 28/183 (15%) individuals colonized on at least one sampling visit. Several individuals tested positive for pneumococcus at multiple time points including two participants who were colonized throughout the 10-week sampling period. Two other adults tested positive at five of the six-time points—one of whom reported daily contact with children aged 2-59 months and 5-9 years," the news release stated.

"Pneumococcal carriage point prevalence (at any sampled time) was substantially (six times) higher among older adults who had contact with children daily/every few days (10%) compared to those who had no contact with children (1.6%)."

The results showed that having recent contact (within the past two weeks) with children under 10 years old, significantly increased the acquisition rate by three times compared to no contact. Similarly, older adults over 60 who had daily or frequent contact with children faced a sixfold higher risk of acquisition than those who had no contact with children.

"Our study found no clear evidence of adult-to-adult transmission even though there were households in which an individual was positive for pneumococcus across numerous sampling moments, and instances where both adults in the household carried pneumococcus around the same time," said lead author Dr Anne Wyllie from the Yale School of Public Health in New Haven.

"Instead, we found that transmission was highest among older adults who had frequent contact with young children. This suggests that the main benefit of adult pneumococcal vaccination is to directly protect older adults who are exposed to children who may still carry and transmit some vaccine-type pneumococcal strains despite successful national childhood vaccination programs," Wyllie said.

Since the inclusion of pneumococcal conjugate vaccines (PCV) in the U.S. childhood vaccination program in 2000, the rates of pneumococcal infections have decreased by over 90% in children. However, the effect has not been seen in older adults.

Based on their current study findings, researchers suggest elderly adults should be vaccinated for pneumococcal infection even in communities where children receive high rates of vaccination.

"If substantial pneumococcal transmission occurs between adults, then vaccination of older adults could have the additional benefit of reducing transmission and potentially serious disease," Wylie said.