Introduction:

Homeless people have a high probability to develop chronic diseases that predispose them to serious complications because of the flu. The objectives of this cross-sectional study were to identify the eligibility criteria and to assess the impact of vaccination against seasonal influenza in homeless people in Lisbon during a vaccination campaign.

Material and methods:

The target population included homeless people from the Lisbon region from 30 November to 6 December 2015. All persons involved gave their consent. We considered statistical significance for a p-value less than 0.01.

Results:

Of the 818 homeless people in Lisbon, 382 (47%) were vaccinated for influenza in the 2015/16 season. Of the 269 homeless people in a row, 179 (67%) had one or more chronic illnesses, 68 (25%) with a clinical history of respiratory infections, but only 19 (28%) had this diagnosis during the winter of 2015-2016. Because of this vaccination campaign, there was a significant reduction in respiratory infections (p<0.01; OR=15.0; CI 5.4-42.3). Of those vaccinated, only three had an influenza A (H1N1) infection with no record of deaths. It was identified that 194 (72% of 269) were eligible for vaccination. Considering the 818 people known to be in this situation in Lisbon, we can extrapolate that 591 would be eligible. It is admitted that more than half of the eligible homeless people in the Lisbon region remained to be vaccinated.

Discussion and conclusions:

It is essential to strengthening flu vaccination campaigns to the homeless population, seeking to find strategies that facilitate referral to surveillance consultations in primary health care, especially if they have chronic diseases.

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