A new study released ahead of the upcoming European Congress of Clinical Microbiology and Infectious Diseases (ECCMID) in Barcelona, Spain, shows that transmission of pneumococcus was highest among older adults who had frequent contact with preschoolers and young school-aged children.
The authors of the small, community-based study say the findings suggest that pneumococcal vaccination in adults could be beneficial even in populations where children are vaccinated at high rates.
Substantially higher pneumococcal carriage
To assess the risks for acquisition of Streptococcus pneumoniae among community-dwelling older adults, researchers from Yale School of Public Health designed a longitudinal study that included 183 adults age 60 and over (mean age 70.9 years) from 93 households with and without young children. Every 2 weeks over a 10-week period across two seasons (November 2020 to August 2021 and November 2021 to September 2022), they obtained saliva samples and questionnaires regarding social behaviors and health status, then used polymerase chain reaction tests to detect pneumococcal DNA.
Overall, 52 (4.8%) of 1,088 samples tested positive for pneumococcus, with 27 (22.3%) of 121 individuals colonized on at least one time point. Several study participants were colonized at multiple time points, including two who were colonized throughout the 10-week sampling period.
The point prevalence of pneumococcal carriage was substantially higher among those who reported contact with children compared with those who reported no contact with children (10.0% vs 1.6%). In addition, 14.8% and 14.1% of participants who reported contact with children aged 5 years and under and those aged 5 to 9 years had pneumococcal carriage, compared with 8.3% of those who reported contact with children over age 10.
Although the numbers were small, participants who had contact with children daily or every few days had the highest prevalence of pneumococcal carriage (15.7% and 14.0%, respectively). There was no clear evidence of adult-to-adult transmission.
"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," lead study author Anne Wyllie, PhD, said in an ECCMID press release.