Lessons from Cuba: mass campaign administration of trivalent oral poliovirus vaccine and seroprevalence of poliovirus neutralizing antibodies.

The immunogenicity of trivalent oral poliovirus vaccine (TOPV), which is less effective in tropical than in temperate areas, may potentially be improved in several ways, including increasing the number of doses. Little information is available on TOPV when more than 6 doses are given. The situation in Cuba provides a unique opportunity to relate the seroprevalence of neutralizing antibodies to the dose of TOPV because Cuba has not reported culture-confirmed poliomyelitis since 1973 and TOPV is only administered in twice yearly 1-week mass immunization campaigns. Sera from 2000 children nationwide were studied for neutralizing antibody among children who received 0, 2, 4, 6 and 8 doses of TOPV. These doses were administered in the period 1989-91, when TOPV (from the USSR) was being used with 500,000, 200,000, and 300,000 median tissue-culture-infecting doses (TCID50) for types 1, 2 and 3, respectively--the 5:2:3 formulation. Seroprevalence of neutralizing antibody after two TOPV doses was 91.5% for type 1, 90.8% for type 2, and 45.9% for type 3. Seroprevalence of type-3 neutralizing antibody after 6 doses remained low (73.4%), but increased to 83.5% after 8 doses (P < 0.05). Although 16.5% of the children remained unprotected for type-3 infection even after 8 doses, mass campaign immunization strategies were sufficient to eradicate the transmission of wild poliovirus in Cuba. Because the seroprevalence of type-1 neutralizing antibody was high (91.5%) after two campaign doses, additional studies using different formulations are needed to determine whether simultaneous improvement in the type-3 response to two campaign doses can be achieved.

PIP: During December 1991-January 1992 in Cuba, health workers took blood samples from a nationwide sample of 2000 children aged 0-3 who received 0, 2, 4, 6, and 8 doses of trivalent oral poliovirus vaccine (TOPV) to determine the seroprevalence of poliovirus neutralizing antibodies for types 1, 2, and 3. Specifically, researchers wanted to learn whether TOPV becomes more effective as the number of doses increases. Since 1973, Cuba has conducted two mass immunization campaigns each year in February and April. During 1970-91, Cuba used a USSR-produced poliovirus vaccine that had 500,000, 200,000, and 300,000 median tissue-culture-infecting doses for types 1, 2, and 3, respectively. Wild poliovirus has not been transmitted in Cuba since 1973 (as of August 1993), indicating that the mass immunization campaigns without routine vaccine delivery have eradicated poliomyelitis in Cuba. The seroprevalence of poliovirus neutralizing antibodies for type 1 increased significantly between 2 and 4 doses (91.5% vs. 96.5%; p = 0.05), thereafter the increases were small and insignificant. The seroprevalence of poliovirus neutralizing antibodies for type 2 increased significantly between 2 and 4 doses (90.8% vs. 97.2%), with small insignificant increases thereafter. Two doses of TOPV induced a response against poliovirus type 3 in only 45.9% of cases. At 4 doses and 8 doses, it did increase significantly from the previous dose (71.2% and 83.5%, respectively; p 0.05). Further studies using other vaccine formulations would allow persons involved in global eradication efforts to determine whether two campaign doses can improve the immunogenicity of the type 3 poliovirus while also improving that of the type 1 poliovirus.

[The infectious etiology of acute diarrheal diseases in the Republic of Cuba, 1991]. / Etiología infecciosa de las enfermedades diarreicas agudas en la República de Cuba, 1991.

This study was carried out in 1991 to learn the behavior of enteropathogenic agents causing acute diarrheal diseases in Cuba. 30 children, admitted in hospitals or seen in outpatient services for acute diarrheal diseases, were selected in each province taking into account that they had not received antibiotic or chemotherapy treatments in the previous 72 hours. Feces samples were taken from all patients for virological, bacteriological, and parasitological studies, and results were sent to the Pedro Kourí Institute of Tropical Medicine. Data were processed in DBASE III. Higher positivity indices were attained in the winter months. The causative agents most frequently found were: rotavirus (8.2%); Entamoeba histolytica (6.1%); and Salmonella (4.2%). Escherichia coli, Campylobacter, Shigella and rotavirus showed higher indices in winter. Shigella flexneri and Shigella sonnei predominated. Salmonella serogroups D, B, and C, and enteropathogenic Escherichia coli 0119 and 026 subsets were the most frequently found.

[Trichuriasis in Cuba]. / Trichuriasis en Cuba.

A representative sample of the Cuban population (11,364) is studied by using Willis and direct coproparasitological techniques. It was found that Trichuris trichiura is the most prevailing intestinal parasite (17.8%). A higher frequency of this kind of geohelminthiasis in people living in Cuban rural zones is seen. A prevalence peak is found in ages from 6 to 9 years, and a higher association of parasitism was found in those with worst hygienic and sanitary conditions.

[Sampling procedure for a survey of an interventional study on acute respiratory infections]. / Procedimiento muestral para una encuesta de un estudio de intervención sobre infecciones respiratorias agudas.

A description is made of the methodology used for obtaining a sample made up of 500 children under 5 years and 500 adults 65 year old and more, in order to carry out an intervention study on acute respiratory tract infections in an urban zone in Havana City and in a rural zone in Matanzas province, where different intervention stops will be taken with regards sanitary education about management of acute respiratory tract infections for the population and training for primary care medical personnel. We show the way the selected sample fits was planned with a very homogeneous distribution in the 8 areas under study, which allows for great reliability in the results.