To study the occurrence of adverse events after administration of a capsular polysaccharide vaccine against 23 pneumococcal serotypes in individuals for whom such vaccination is indicated. This was a prospective study, conducted in a general hospital in the city of Sumaré, in which 152 individuals were evaluated after intramuscular vaccination with 0.5 mL of the Pneumo 23 vaccine. The study variable was subject complaint of at least one symptom forming a temporal nexus with the vaccine (appearing within 48 h after its administration). The subjects were evaluated at five to seven days after vaccination. The covariables age, gender and clinical profile were tested using the chi-square test and multiple logistic regression, with the level of significance set at 5%. The age of the population ranged from 5 to 86 years (mean, 61.8 years). For nearly all (99%) of the subjects, the vaccination evaluated was their first dose of the vaccine. Events occurring at the injection site were reported in 36 subjects (23.7%). Of those 36 events, 24 (68%) were mild and had no repercussions for the daily activities of the subjects. Pain at the site of the injection was the most common symptom, being reported by 97.2% of the subjects. Erythema and localized edema were found in 6.3% and 5.1% of the subjects, respectively. Of the subjects evaluated, 12.8% reported general symptoms (malaise, fever, sleepiness and generalized pain). In the bivariate analysis, none of the covariables were found to present a statistically significant correlation with adverse events (p > 0.20). The same held true in the multivariate analysis. Although, the 23-valent pneumococcal vaccine provokes few reactions in the first dose, it is still rarely recommended in the region, even for patients at risk.3351-6