Rapid Rise in Pneumocystis Pneumonia Threatens Immunocompromised Population

Pneumocystis pneumonia as a proportion of all hospital admissions rose by 84% from 2012 to 2022 — from 6.5 to 11.3 episodes per 100,000 admissions.

The rapid rise in the incidence of pneumocystis pneumonia (PCP) that has occurred over the last decade represents a significant threat to those who are immunocompromised, according to study findings published in the Journal of Infection.

As a complication of human immunodeficiency virus (HIV) infection, PCP rose to distinction during the 1980s and remains a significant illness among the immunocompromised population, with mortality among non-HIV patients reaching almost 53%. Investigators sought to assess the population-level incidence of PCP since 2012.

This population-level descriptive study conducted in the United Kingdom drew data from electronic health records (from the Hospital Admitted Patient Care Activity Records, part of the National Health Service Hospital Episode Statistics database) of patients admitted to hospitals throughout England from April 2012 through March 2022. Deidentified data collection included sex, age, length of stay, PCP episodes, and other respiratory fungal infections. Investigators also collected data on the consumption of trimethoprim-sulfamethoxazole from January 2019 through April 2022.

The researchers found an increasing incidence of PCP between 2012/2013 (2.2/100,000 people) and 2019/2020 (4.5/100,000) (P <.0001). Incidence rates have fluctuated since, dropping in 2020/2021 (2.7/100,000) and rising in 2021/2022 (3.9/100,000). Additionally, PCP episodes accounted for a rising proportion of admissions for disseminated or respiratory fungal infections and admissions involving all-cause mortality. During the same time, there was an 11% increase in all-cause admissions per 100,000 people. PCP as a proportion of all-cause hospital admissions increased by 84% from 2012 to 2022 (from 6.5 episodes/100,000 to 11.3 episodes/100,000). Trends were consistent with PCP as a primary or secondary diagnosis.

The proportion of older patients (>74) affected by PCP increased significantly from 2012 (14%) to 2021 (26%) (P <.0001). Mean age increased significantly in the same time period from 59 years to 61 years (P <.005). The mean number of cases with men was 61% across all years.

Our study shows that the incidence and impact of PCP is increasing and must serve as a reminder to clinicians that PCP remains a threat to the immunocompromised population.

Trimethoprim-sulfamethoxazole consumption increased from 2.14/100,000 to 2.74/100,000 defined daily doses. Investigators noted a step reduction between April 2020 and April 2021 of consumption of intravenous co-trimoxazole, corresponding to the first year of the COVID-19 pandemic in England. Oral preparations revealed a similar pattern.

The median length of hospital stay for PCP was 13.5 days (range, 12-15 days), compared with 1 day for all-cause admissions. Investigators noted there was no significant difference in length of stay over time (P =.062).

Significant study limitations include the inability to verify the validity of diagnoses at an individual level and the effect of unknown factors such as the number of patients having PCP more than once, the number of patients prescribed and taking prophylaxis, and how PCP was diagnosed. Additional limitations include researchers’ limited ability to make inferences about morbidity or mortality due to unknown outcomes of patients with PCP, and potential overestimation of co-trimoxazole use (because numbers were derived from hospital purchasing data which did not indicate whether the drug was being used for PCP).

The study authors concluded that “Our study shows that the incidence and impact of PCP is increasing and must serve as a reminder to clinicians that PCP remains a threat to the immunocompromised population.” Although effective and safe prophylaxis is available, and a Cochrane review suggested prophylaxis be used for patients with baseline risk of 6.2%, there is nevertheless a lack of agreement on who should receive it, they noted.

Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.


Pates K, Periselneris J, Russell MD, Mehra V, Schelenz S, Galloway JB. Rising incidence of pneumocystis pneumonia: A population-level descriptive ecological study in England. J Infect. Published online February 10, 2023. doi:10.1016/j.jinf.2023.02.014