Sequential and combined use of inactivated and oral poliovirus vaccines: Dolj District, Romania, 1992-1994.

To determine the feasibility of a vaccination strategy that would reduce the risk of vaccine-associated paralysis while retaining a barrier against the spread of wild poliovirus, a 2-year project was undertaken using enhanced-potency inactivated poliovirus vaccine (IPV) administered at 2 and 3 months of age followed by doses of both IPV and oral poliovirus vaccine (OPV) administered at 4 and 9 months of age. Vaccination coverage by 12 months of age with three or more doses of IPV and two doses of OPV among 16,566 infants eligible for vaccination was > 95% and > 80%, respectively. Among 51 children from whom blood samples were obtained 45 days after their third dose of IPV and first dose of OPV, 100% had serum neutralizing antibodies (reciprocal titer > or = 10) to all three poliovirus types.

Paralytic poliomyelitis in Romania, 1984-1992. Evidence for a high risk of vaccine-associated disease and reintroduction of wild-virus infection.

Although poliomyelitis due to wild-virus infection has virtually disappeared from Romania, with no cases having been documented between 1984 and 1989, vaccine-associated paralytic poliomyelitis has been reported at very high rates for over two decades. In November 1990, to decrease the risk of vaccine-associated paralytic poliomyelitis, oral poliovirus vaccine produced in Romania was replaced by imported oral vaccine made by a Western European manufacturer. To better quantify the risk of vaccine-associated paralytic poliomyelitis and the impact of the change in vaccine manufacturer, the authors reviewed clinical, epidemiologic, and laboratory data on poliomyelitis cases that occurred in Romania from 1984 to 1992.

Serosurvey for polio antibodies.

From 1982 to 1988 a serological survey was performed on 573 subjects aged 3-80 years in order to evaluate the polio immunity level of the population. The presence of neutralizing antibodies was tested using the types 1, 2 and 3 Sabin vaccine strains as well as a wild strain of poliovirus type 1 isolated in France in 1978. According to their birth date, the subjects were assigned to 4 groups.

Optimum age for measles immunization in Romania.

From 1979 to 1985 a serological survey was carried out to evaluate the opportunity to start measles vaccination at the age of 9 months. The following aspects were investigated: the persistence of maternal measles antibodies in 188 infants aged 1-8 months: such antibodies could not be detected over 7 months of age; the antibody response to measles vaccination in 181 infants vaccinated at the age of 9-11 months versus 291 children vaccinated when aged more than 12 months: no significant differences were found between the two groups; the age-specific persistence of vaccine-induced hemagglutination-inhibiting antibodies during the 1-4 years following vaccination: no significant difference was found in terms of the children's age upon vaccination. The results lend support to the recommendation to consider 9 months as a satisfactory age to initiate measles immunization in Romania.

WHO collaborative studies on poliovirus type 3 strains isolated during the 1968 poliomyelitis epidemic in Poland.

In 1968 in Poland an extensive outbreak of poliomyelitis, caused by type 3 poliovirus, began about four months after small vaccine trials with the Leon 12a(1)b (Sabin) and USOL-D bac vaccine strains had been carried out. Because of the temporal association, and because the first cases appeared in the province in which the USOL-D vaccine trial was carried out, a detailed investigation of the strains isolated from cases in the epidemic was made in four laboratories in an attempt to determine whether they were related to the two vaccine strains or to a "wild" strain. All the studies were made under code.