During a large community-wide outbreak of hepatitis A in two adjoining villages in Slovakia with a total of 5,000 inhabitants we administered to schoolchildren the first commercially available vaccine against hepatitis A (HAVRIX, Smith-Kline Beecham Biologicals, Rixensart, Belgium) in an attempt to control the progress of the epidemic. Soon after the start of the vaccination programme, an abrupt decrease in the occurrence of cases in the school was observed. In the village school with 624 schoolchildren, 404 had received a first dose of 360 enzyme-linked immunosorbent assay (ELISA) units (EL.U) and 373 a second dose 1 month later. Subsequent to the start of vaccination there were eight clinical cases of hepatitis A among the 157 children without a history of hepatitis A who remained unvaccinated and only 1 case in the vaccinated school children, giving attack rates of 5.1% and 0.25% in the two groups, respectively. Among the remaining 63 children, one was found seropositive when screened and 62 had a history of hepatitis A at the start of the vaccination programme. These 63 children were not offered vaccine. No cases occurred in that group. During the epidemic, three cases occurred an average of 20 days following its administration among 19 children who received immune globulin (IG). Cases in the whole population of the villages also ceased soon after the vaccination of the children had started. The vaccine was found more effective than postexposure IG in interrupting the epidemic in the whole community.

We assessed the long-term persistence of humoral immunity against diphtheria in adults with childhood vaccination and the immunogenicity of a booster dose considering demographic, behavioural and vaccinating factors. We conducted a trial in 200 healthy Slovak adults aged 24–65 years, immunised against diphtheria in childhood and against tetanus at regular 10–15 year intervals, and receiving a dose of a tetanus-diphtheria toxoid vaccine. The response was determined by ELISA antibody concentrations of paired sera before and at 4 weeks post-vaccination. A seroprotection rate of 21% (95% confidence interval, CI 15.6–27.3%) was found in adults up to 59 years since the last vaccination with seroprotective levels of antibodies against diphtheria ≥0.1 IU/mL and a geometric mean concentration of 0.05 IU/mL. Conversely, seropositive levels ≥0.01 IU/mL were observed in 98% of adults (95% CI 95–99.5%). Booster-induced seroprotection was achieved in 78% of adults (95% CI 71.6–83.5%) clearly depending on pre-booster antibody levels correlating with age and time since the last vaccination. Moreover, only 54.2% of smokers and 53.3% of patients on statins exhibited seroprotection. Booster vaccination against diphtheria was unable to confer seroprotection in all recipients of only childhood vaccination.

An evaluation of the relationship between predictors and immune response was conducted using data obtained from a clinical trial in 200 Czech healthy adults aged 24-65 years receiving a booster dose of a monovalent tetanus vaccine in 2017. The response was determined from ELISA antibody concentrations of paired sera obtained before and 4 weeks after the immunisation. While all subjects with initial antibody levels 2.2 IU/ml. The immune response was not affected by sex, age, tetanus vaccine type, concomitant medication, related adverse events or post-vaccination period since there were no significant differences in geometric mean concentrations or seroconversion rates. The seroconversion rate of 56% in smokers was significantly lower than that of 73% achieved in non-smokers. Although the seroconversion rates did not differ between individuals with normal or higher body weight, the adjusted odds ratio (1.3; 95% Cl 1.08-1.60) revealed a positive correlation between seroconversion rate and body mass index (BMI). Although the vaccine-induced response was influenced by pre-vaccination antibody levels, smoking or BMI, the booster immunisation against tetanus produced a sufficient response regardless the predictors.

Owing partly to a lack of disease burden data, Eastern and Central European countries have not introduced universal infant immunization against Haemophilus influenzae type b. To determine the incidence of Haemophilus influenzae type b meningitis among children less than 5 years of age, data were examined from eight districts in Slovakia that formed part of a national Haemophilus influenzae type b surveillance system. All invasive isolates of Haemophilus influenzae type b identified from these districts during 24 months (1996-1997) were sent to a single central laboratory for serotype confirmation. Thirty-five cases of confirmed Haemophilus influenzae type b meningitis were identified, for a disease incidence among children under 5 years of 17.3 per 100,000 population per year. Only 13 cases were identified during 1996, the first full year of the surveillance system. Records were available for review at six of the eight district laboratories and showed that, using World Health Organization definitions, almost half of the cases of probable bacterial meningitis were culture negative, suggesting that the true incidence of Haemophilus influenzae type b meningitis may be considerably higher than 17.3. The rate of Haemophilus influenzae type b meningitis among children less than 5 years of age in Slovakia is comparable to that found in Western Europe and North America during the prevaccine era. Thus, universal, publicly funded infant vaccination in Slovakia can be expected to have the same dramatic effect on Haemophilus influenzae type b disease morbidity and mortality as has been demonstrated in other countries that have adopted this approach.

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