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Backgrounds. Severe trauma of the spleen can be followed by excessive internal bleeding. The life of the injured person can be saved only with splenectomy. Removal of the spleen reduces resistance of the patient to infections, most frequently those caused by pneumococci. The most effective way of protecting these patients is vaccination with a 23-valent pneu­mococcal vaccine. The aim of our research was to establish at what time after splenectomy vaccination is most effective. Different possibilities were studied: vaccination just before splenec­tomy, vaccination one day after and seven days after splenectomy. Our hypothesis was that vaccination just before splenectomy has the best protective effect from infection.

Methods. The prospective study was carried out on thirty mice divided into six groups. Their spleens were surgically removed and they were vaccinated at different times before or after the operation. The first group was vaccinated, without splenectomy. The second group was vaccinated just before splenectomy, the third group 1 day after and the fourth group 7 days after surgery. The fifth group had their spleens removed without vaccination. The sixth group consisted of healthy, unvaccinated mice. During the study, the mice had their blood drawn four times. With an enzyme-linked immunosorbent assay, the changing of the amount of spe­cific IgM and IgG antibodies directed against pneumococcal antigens was measured. The amount of precipitating antibodies in the blood serum of mice was measured with a micro­precipitation capillary test. The study was concluded with a supervised infection of mice with live pneumococci.

Results. The amount of IgG, IgM and precipitating antibodies was at all times highest in the group of immunized unsplenectomized mice (group 1). A statistically significant difference was found between this and all other groups (p < 0.05). Between the splenectomized groups of mice, mice immunized 1 day after splenectomy (group 3) produced the highest amount of specific antibodies against Streptococcus pneumoniae. However there was no statistically significant difference found between group 3 and the group of mice immunized just before splenectomy (group 2) (p > 0.05). The lowest amount of specific antibodies was produced in the group of mice immunized 7 days after splenectomy (group 4). There was a statistically significant difference found between group 4 and other groups of immunized mice (p < 0.05). Simmular results were obtained after a supervised infection of mice with live pneumococ­ci. Four out of five mice died in the group of healthy mice (group 6) and in group 4. No mice died in the groups of only vaccinated mice and mice vaccinated just before splenectomy. Inspite of the high quantity of specific antibodies in the group of mice vaccinated 1 day after splenec­tomy, two out of five mice died.

Conclusions. We conclude that vaccination with a pneumococcal vaccine triggers synthesis of specific antibodies. Splenectomy lowers the ability of this synthesis. The lowering depends on the time between splenectomy and vaccination. The highest ability of synthesis of spe­cific antibodies was in operated mice vaccinated just before and 1 day after surgery. Our results confirm the hypothesis that vaccination with a pneumococcal vaccine is most effective if mice are vaccinated just before or very soon after splenectomy.