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Fact check: Is there actually a study from 2019 showing increased risk of pneumonia and death with pneumococcal vaccines
Executive Summary
A 2019 Catalonia population-based cohort study is widely cited as finding that receipt of PCV13 and PPSV23 was associated with higher rates of hospitalized pneumococcal pneumonia and all-cause pneumonia, and with increased pneumonia-related deaths; that specific study is summarized in multiple later reports [1] [2]. Larger and more recent syntheses and national reviews tell a more mixed story: randomized trials, ecological studies of infant PCV programs, and meta-analyses show substantial reductions in invasive pneumococcal disease and pediatric pneumonia hospitalizations, while adult vaccine effectiveness for non-bacteremic pneumonia and mortality remains variable across settings [3] [4]. The evidence therefore contains an apparent contradiction between a notable 2019 Catalonia cohort finding and broader literature showing net public-health benefits from pneumococcal vaccination programs.
1. The Catalonia 2019 finding that grabbed headlines and why it matters
The Catalonia cohort reported no measurable clinical effectiveness of PPSV23/PCV13 against hospitalized pneumococcal pneumonia (PP) or all-cause pneumonia (ACP) in adults aged ≥50, and found that vaccinated individuals had higher adjusted risks of PP and ACP compared with unvaccinated people [1]. That result matters because it appears to contradict vaccine policy assumptions and randomized-trial evidence for certain endpoints, and because observational cohort designs can generate strong signals that attract media and policy attention. The study authors adjusted for age, sex, comorbidities and influenza vaccination in attempting to control confounding, but observational analyses are vulnerable to residual bias: vaccinated people may differ from unvaccinated people in healthcare-seeking behavior, unmeasured frailty, or timing of vaccination relative to disease exposure, which can produce counterintuitive associations even when vaccines are beneficial [5] [2].
2. Large-scale and randomized evidence that points in a different direction
Multiple sources synthesize evidence showing that pneumococcal conjugate vaccines (PCVs), particularly when used in infant schedules, produce clear declines in invasive pneumococcal disease (IPD) among both vaccinated children and unvaccinated adults through herd effects, and correspond with reductions in pediatric pneumonia hospitalizations in the United States and elsewhere [3]. Systematic reviews and meta-analyses of adult vaccination and observational studies yield heterogeneous results: while some analyses find reductions in all-cause hospitalization or IPD, effectiveness against non-bacteremic pneumonia and mortality is inconsistent across populations and study designs [4]. This broader literature indicates population-level benefits from PCV introduction, even if individual adult effectiveness estimates vary.
3. Why observational studies can show higher risk among vaccinated people
Observational cohort studies sometimes show apparent increased risk of outcomes among vaccinated groups because of confounding by indication and selection effects: people with more comorbidities or higher baseline risk are more likely to be offered and to accept pneumococcal vaccines, creating an association between vaccination and subsequent adverse outcomes that does not reflect causation [5] [2]. Even with statistical adjustment, residual confounding from unmeasured frailty, health-care utilization, or misclassification of outcomes can remain. Conversely, ecological declines in IPD after infant PCV programs reflect population-level herd immunity less susceptible to individual-level confounding, which helps explain the divergence between some cohort results and the macro-level public-health evidence [3] [4].
4. What multiple recent analyses and reviews conclude when taken together
Recent syntheses present a mixed but largely favorable picture for pneumococcal vaccination at the population level: PCVs have markedly reduced vaccine-type invasive disease and pediatric pneumonia hospitalizations, while adult vaccine impacts on non-invasive pneumonia and mortality are inconsistent and context-dependent [3] [4]. The Catalonia 2019 cohort contributes an important cautionary datapoint that adult effectiveness can be limited in routine practice and that observational signals of harm need careful scrutiny for bias [1]. Policy bodies continue to update recommendations toward higher-valency PCVs for adults, reflecting evolving serotype coverage and continual reassessment of benefit-risk in different age and risk groups [6].
5. Bottom line for readers asking “Is the 2019 study real and definitive?”
Yes—the 2019 Catalonia population-based study exists and reported no clinical effectiveness of PPSV23/PCV13 for the measured adult endpoints and an association of vaccination with increased pneumonia outcomes; that study is cited in several later summaries [1]. The study is not definitive on causation: its observational design makes it susceptible to residual confounding and selection bias, and its findings sit alongside randomized and ecological evidence showing clear reductions in invasive disease and pediatric hospitalizations after PCV use [3] [4]. Interpreting vaccine effects requires weighing cohort signals, randomized trials, population-level trends, and potential biases together rather than treating any single study as conclusive.