PCV13 Prevents Medically Attended Pneumococcal LRTI in Older Adults

The pneumococcal 13-valent conjugate vaccine (PCV13, Prevnar 13; Pfizer) demonstrated real-world effectiveness in preventing medically attended pneumococcal lower respiratory tract infection (LRTI) among older adults in Thailand, according to new data published by study investigators in Scientific Reports.¹

What Role Does PCV13 Play in Thailand’s National Vaccine Strategy?

In 2013, the CDC and Advisory Committee for Immunization Practices (ACIP) recommended the routine use of PCV13 in series with the 23-valent pneumococcal polysaccharide vaccine (PPSV23) for adults aged 65 and older. Although the serotypes constituting those targeted by PCV13 have dissipated in prevalence—therefore no longer necessitating a broad recommendation for adults—PCV13 is still recommended for all older adults who have not previously received it. Shared clinical decision-making for adults who do not have an immunocompromising condition is recommended when considering PCV13 vaccination.^1,2

Pneumococcal disease remains a scourge globally, classified as a leading cause of hospitalized community-acquired pneumonia (CAP) among older adults. Vaccination with PCVs has reduced such a burden, but although numerous studies have evaluated and affirmed the real-world effectiveness of PCVs, uptake in low- or middle-income countries (LMIC) is more limited.¹

In Thailand specifically, more work is necessary to increase pneumococcal vaccine uptake. For children, PCV has been recommended in national guidelines, but it is considered optional for high-risk adults, limiting uptake in this population. This is in spite of the fact that common pneumococcal serotypes in Thailand are included in those targeted by the PCV13 vaccine, and research that the vaccine is a cost-effective option compared with either PPSV23 or no vaccination.^1,3

To better inform national vaccine policy in both Thailand and other LMICs, greater efforts to uncover real-world evidence on the effectiveness of PCV13 is necessary. LRTI is an especially serious presentation of Streptococcus pneumoniae. It contributes to high mortality rates in older adults due to severe cough, high fever, fatigue, chest pain, and breathing difficulties. Therefore, the current authors sought to evaluate PCV13’s effectiveness at preventing medically attended LRTI in older adults.^1,4,5

How Effective Was PCV13 at Reducing LRTI in Older Adults?

In the case-controlled study (NCT06279624), data of adults aged 60 years and older was retrospectively collected from Siriraj Hospital, a major university-affiliated hospital in Bangkok, Thailand. Vaccination status was determined based on documentation of a PCV13 dose more than 2 weeks prior to the date of medical attendance for LRTI. In total, 275 patients whose samples yielded Streptococcus pneumoniae and 550 control patients admitted to Siriraj Hospital between January 2014 and December 2024 were included in the analysis.^1,6

The authors first analyzed characteristics of pneumococcal LRTI. Admissions to an intensive care unit were observed in 20.5% of PCV13-vaccinated patients compared with 35.2% of controls. There was a lesser requirement for mechanical ventilation at admission among patients who received PCV13 compared with unvaccinated controls (20.0% versus 54.1%). Importantly, all patients with pneumococcal LRTI and vaccinated with PCV13 were discharged without in-hospital mortality, compared with a 19.3% mortality rate in unvaccinated individuals.¹

According to a crude analysis, PCV13 was tied to a statistically significant reduction in the odds of medically attended pneumococcal LRTI (OR = 0.28; 95% CI, 0.11–0.73). This corresponded with an estimated vaccine effectiveness (VE) of 71.9% compared with unvaccinated patients. Following adjustments for confounders, the association remained significant (aOR = 0.27; 95% CI, 0.08–0.91), providing an adjusted VE of 73.3%.¹

Stratified analyses were employed to assess interactions by age group. These suggested that VE against pneumococcal LRTI was comparable between individuals aged 75 and older (VE = 59.9%) and those aged less than 75 years (VE = 57.4%), confirming the benefits of vaccination for a broad swath of older adults.¹

These results affirm the effectiveness of vaccination in older adults from Thailand and could help further proliferate PCV13 among at-risk patients. LMICs could especially benefit from more thorough vaccination campaigns, as pneumococcal disease remains a major burden across the globe.¹

“Continued disease surveillance and re-evaluation of vaccine effectiveness are essential, especially in countries where the introduction in children has already existed and has achieved high coverage,” the study investigators concluded.¹

REFERENCES

1. Ngamprasertchai T, Phatharodom P, Intalapaporn K, et al. Effectiveness of the 13-valent pneumococcal conjugate vaccine against medically attended pneumococcal lower respiratory tract infection among older adults: a case–control study. Scientific Reports. 2025;15:40997. doi:10.1038/s41598-025-24784-0

2. Thewjitcharoen Y, Butadej S, Malidaeng A, et al. Trends in influenza and pneumococcal vaccine coverage in Thai patients with type 2 diabetes mellitus 2010-2018: Experience from a tertiary diabetes center in Bangkok. J Clin Transl Endocrinol. 2020;20:100227. doi:10.1016/j.jcte.2020.100227.

3. Evidence to recommendations for PCV13 use among adults ≥ 65 years old. CDC—ACIP. Last Updated September 5, 2024. Accessed December 3, 2025. https://www.cdc.gov/acip/evidence-to-recommendations/PCV13-etr.html

4. Yu X, Yang X, Song Y, et al. Lower respiratory tract co-infection of Streptococcus pneumoniae and respiratory syncytial virus shapes microbial landscape and clinical outcomes in children. Front Cell Infect Microbiol. 2025;9(15):1593053. doi:10.3389/fcimb.2025.1593053

5. Mahashur A. Management of lower respiratory tract infection in outpatient settings: Focus on clarithromycin. Lung India. 2018;35(2):143-149. doi:10.4103/lungindia.lungindia_262_17

6. Effectiveness of the PCV13 in older Thai adults. ClinicalTrials.gov Identifier: NCT06279624. Last Updated May 9, 2025. Accessed December 3, 2025. https://clinicaltrials.gov/study/NCT06279624