LOS ANGELES (CNS) — A Kaiser Permanente Southern California study showed that one type of pneumonia vaccine may affect the course of COVID-19 for some older adult patients, it was announced Wednesday.

"Kaiser Permanente members who received the PCV13 vaccine appeared to be diagnosed with COVID-19 less often, and when they were, they seemed to have less severe outcomes, overall," said the study's senior author, Dr. Sara Tartof, a scientist with Kaiser's Department of Research & Evaluation. "One of the most interesting aspects of our findings was that the patients who received PCV13 received some protection against COVID-19, while those who received PPSV23, another pneumococcal vaccine, did not."

When the coronavirus infects a new person, it encounters a diverse array of viral and bacterial species that naturally reside in the human upper airway. One of these species is a bacterium called Streptococcus pneumoniae, or pneumococcus, which is commonly carried by children as well as adults, researchers said. While typically harmless, this bacterium is well known for causing pneumonia and other diseases, often in interaction with viruses.

The Kaiser study — published in The Journal of Infectious Diseases — provides evidence that these bacterial-viral interactions may play out in ways that shape the course of COVID-19, according to the medical group.

While the recently authorized COVID-19 vaccines remain the most important strategy for preventing the disease, investigators found that older adults who received pneumococcal conjugate vaccine (PCV13), which prevents acquisition of certain pneumococcal strains, experienced 35% lower risk of COVID-19 diagnosis than adults who did not receive the vaccine. In contrast, an alternative pneumococcal vaccine (PPSV23), which prevents severe pneumococcal disease but does not block acquisition of the bacterium, was not associated with protection.

The study examined electronic health records of 531,033 members of Kaiser Permanente in Southern California who were 65 years old and older from March 1 to July 22, 2020. Among that population, 3,677 had a COVID-19 diagnosis, 1,075 were hospitalized for COVID-19, and 334 died from COVID-19.

Those who received PCV13 had 35% lower incidence of COVID-19 diagnosis, 32% lower incidence of COVID-19 hospitalization, and 32% lower incidence of COVID-19 death, the study showed.

Anyone can get pneumococcal disease, but children under 2 years of age, people with certain medical conditions, cigarette smokers, and adults aged 65 years or older are at the highest risk. The study's authors only looked at older patients, who also face the highest risk of severe COVID-19.

PCV13 protects against 13 types of bacteria that cause pneumococcal disease. This vaccine is given to adults 65 or older based on shared decision-making between the patient and health care provider, typically based on risk factors. These risk factors, which can include COPD, asthma, heart disease, are also factors that can put people at risk for COVID-19.

"Over the years we have learned that pneumococci interact with influenza, RSV, and several other viruses in the airway," said lead author Dr. Joseph Lewnard, of the School of Public Health at UC Berkeley. "These observations with SARS-CoV-2 help to suggest that the phenomenon may be more general than we have previously appreciated."