Pneumonia is a common complication of influenza in elderly patients, causes a significant increase in morbidity and mortality, and can potentially be prevented by vaccination. However, despite the fact that vaccination can reduce the risk of developing pneumonia, the possible success of vaccination in elderly patients is currently controversial.

Previous randomized trials have confirmed that vaccination reduces the risk of influenza in healthy older adults aged 60 years and older, but these studies have not considered the effect of influenza vaccination in the general population. patients over the age of 65, many of whom have concurrent chronic conditions.

The study, led by researchers from Seattle (Washington, USA), was a large population-based case-control study aimed at determining whether influenza vaccination reduced the risk of developing pneumonia. community origin in immunocompetent elderly people.

The study population included immunocompetent elderly patients aged 65 to 94 (1,173 study patients and 2,346 controls) using the services of the healthcare organization Group Health * during influenza seasons and previous periods in 2000, 2001 and 2002. Patients included in the study population were defined as individuals with community-acquired pneumonia who received treatment both in the outpatient setting and in the hospital. For each of them, 2 control patients were randomly selected, comparable by age and sex. Data on the presence of pneumonia were confirmed by information from medical records or by results of chest x-rays.

In 752 patients (64%), community-acquired pneumonia was treated on an outpatient basis, 447 patients (38%) were less than 75 years old, 531 patients (45%) aged 75 to 84 years and 195 people (17% ) 85 years and over; 597 patients (51%) included in the study were men.

The flu vaccination was voluntary. Data on decreased physical activity, muscle pain, decreased performance, fatigue and reduced endurance, inexplicable weight loss, presence and severity of heart and lung disease, history of smoking and other potentially unwanted factors were collected according to medical records.

When assessing patients, they took into account age, gender, presence of asthma, history of smoking, appointment of antibiotics for lower respiratory tract infections that differ from normal volume results forced expiratory in one second (FEV1), the use of oxygen at home, the use of inhaled and oral glucocorticoids, bronchodilators, statins, antipsychotropics, as well as any visit to an optometrist or ophthalmologist.

After assessing the presence and severity of concurrent conditions in patients, it has been found that vaccination against influenza does not reduce the risk of developing community-acquired pneumonia during the influenza season (risk ratio (RR) 0 , 92; 95% CI 0.77-1.10). For patients hospitalized during the influenza period, the risk ratio was 0.85 (95% CI 0.62-1.15; p = 0.28). For 246 pneumonia patients admitted to hospital during the peak season, the risk ratio was 1.41 (95% CI 0.35-3.02; p = 0.39).

Thus, the effect of influenza vaccination on the risk of developing pneumonia in the elderly during the flu season may be less than previously thought.

At the same time, these data may be biased due to concomitant differences in the assessment of health indicators between groups. In addition, most people with pneumonia are hospitalized and information about them should also be included in these studies. The limitations of this study may also be possible inaccuracies in classifying patients based on immunization status, as some patients included in the study may have been vaccinated outside of the Group Health organization.

More complete information on the effects of antigenic interaction and other factors affecting the efficacy of the vaccine in elderly patients can be obtained by conducting studies that use laboratory-confirmed results and take into account a wider range of undesirable conditions. However, even despite the optimal study design, interpretation of the vaccine efficacy results may be difficult when performing observational studies in elderly patient populations due to the high percentage of vaccines in old people. In addition, when a small part of the population prefers not to be vaccinated, no other undesirable factor can be excluded.