The PPV23 vaccine, designed to protect against community-acquired pneumonia (CAP) caused by Streptococcus pneumoniae, is not uniformly effective among the general population, immuno-compromised individuals and those with underlying risk factors, according to results of a new review.
The study, “Effectiveness of pneumococcal vaccines in preventing pneumonia in adults, a systematic review and meta-analyses of observational studies,” appeared in the journal PLoS One. Its authors called for increased monitoring of vaccine effectiveness in adults, as well as better vaccination coverage in children.
“S. pneumoniae can cause a wide spectrum of diseases, including invasive pneumococcal disease and pneumonia,” researchers wrote. “Two types of pneumococcal vaccines are indicated for use in adults: 23-valent pneumococcal polysaccharide vaccines (PPV23) and a 13-valent pneumococcal conjugate vaccine (PCV13).”
Researchers reviewed 33 previously published studies evaluating the effectiveness of pneumococcal vaccine against CAP among adults in general, among immuno-compromised individuals, and among people with chronic obstructive pulmonary disease, chronic respiratory diseases and other underlying risk factors. The analysis retrieved no studies evaluating the effectiveness of PCV13.
In contrast, estimates of PPV23 effectiveness in adults aged 65 or older were not consistent, while its effectiveness for CAP cases requiring hospitalization among the general population was 10.2 percent. It was also significantly lower among patients who had been vaccinated for five years or more compared to those who had received a vaccine more recently. Vaccine effectiveness is also lower in countries in which the PCV vaccine for children is available privately.
“Overall, the effectiveness of PPV23 against CAP has not been consistently demonstrated in the general population (including the elderly), the immunocompromised and subjects with underlying risk factors,” researchers wrote. “This lack of consistency may be related to a great diversity of study populations, circulation of S. pneumoniae serotypes, and coverage of pneumococcal pediatric vaccination.”
They added: “Pneumococcal vaccination programs, both adult and pediatric programs as an integrated public health intervention are likely to impact the proportion of CAP caused by S. pneumoniae and thus influencing the effectiveness of the vaccines evaluated. Monitoring of adult pneumococcal [vaccine effectiveness] should continue in the context of increasing PCV13 use in adults and increasing vaccination coverage in the pediatric population.”