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Booster doses of MMR vaccine equal in dosage to injected doses were aerosolized into a 3/4 l bag that inflated in 4s. The bag was then attached to valved masks, and its contents rapidly inhaled in one or two deep breaths by preschool Mexican children. Antibody responses in the children exposed to the aerosolized measles component were superior to those noted after injection, while responses to the mumps and rubella components were equivalent. The new method appears to be effective, safe, and has several advantages over previously used methods. Further explorations of the approach seem merited.

The purpose of the present study was to compare serum and mucosal immune responses following either aerosol (Aer) or subcutaneous (SQ) measles immunization of Mexican school children. A cohort of 49 children from 6 to 7 years of age received either Aer ( n = 22) or SQ ( n = 27) Edmonston-Zagreb (EZ) measles vaccine. Serum and nasal secretions were collected prior to (Pre), 1 and 3 months (mos) intervals and analyzed for immunoglobulin (Ig) concentrations and measles specific Ig isotype-associated antibody by enzyme immunoassay (EIA). Serum and nasal IgG and IgA antibody responses were stimulated following immunization with live, attenuated EZ measles vaccine administered either by SQ or Aer routes but these responses were significantly greater by the Aer compared to the SQ route. These studies also suggest that the level of antibody in these secretions may serve as an important marker of immunity to measles and lend further support for aerosol immunization as an effective alternative vaccine delivery strategy for measles eradication.

Objective: To compare antibody responses and side-effects of aerosolized and injected measles vaccines after revaccination of children enrolling in elementary schools., Methods: Vaccines for measles (Edmonston-Zagreb) or measles-rubella (Edmonston-Zagreb with RA27/3) were given by aerosol or injection to four groups of children. An additional group received Schwarz measles vaccine by injection. These five groups received vaccines in usual standard titre doses. A sixth group received only 1000 plaque-forming units of Edmonston-Zagreb vaccine by aerosol. The groups were randomized by school. Concentrations of neutralizing antibodies were determined in blood specimens taken at baseline and four months after vaccination from randomized subgroups (n = 28-31) of children in each group., Findings: After baseline antibody titres were controlled for, the frequencies of fourfold or greater increases in neutralizing antibodies did not differ significantly between the three groups that received vaccine by aerosol (range 52%-64%), but they were significantly higher than those for the three groups that received injected vaccine (range 4%-23%). Mean increases in titres and post-vaccination geometric mean titres paralleled these findings. Fewer side-effects were noted after aerosol than injection administration of vaccine., Conclusion: Immunogenicity of measles vaccine when administered by aerosol is superior to that when the vaccine is given by injection. This advantage persists with aerosolized doses less than or equal to one-fifth of usual injected doses. The efficacy and cost-effectiveness of measles vaccination by aerosol should be further evaluated in mass campaigns.

The present work describes the anti-measles vaccination program by the inhaled aerosol method undertaken in Mexico between 1988 and 1990. Detailed descriptions are given of the equipment, staff, training programs, promotion and campaigns. The vaccine is specified: Edmonston-Zagreb strain cultured in diploid cells at the Instituto Nacional de Virología of the Secretaría de Salud in Mexico with titres varying from 1045 plaque forming units (PFU/ml) to 1048 PFU/ml administered in a 30 sec inhalation with aerosol. During this exposure period, 2800 to 4000 PFU per child are estimated to enter the child, of which approximately 25% is the retained doses, i.e. 700 to 1000 PFU/child. A total of 3760684 children of school and pre-school age have been vaccinated in 13 of the 32 federal entities of the country. No undesirable effects of any importance were observed, and the limited serological and field studies support the effectiveness and security of this method. On the other hand, the method is much cheaper, faster and better accepted by the population than the subcutaneous injection.

This paper discusses the right to health in Mexico. The authors present some ideas regarding equity and data which shows the existence of a deep inequity in the field of health in the country. The efforts of the social security agencies and of the Ministry of Health aimed at diminishing inequity in health are also described. The authors conclude that it is time to avoid retorical positions and attitudes of administrative solidarity and start to implement actions to improve the health conditions of those living in extreme poverty. These actions should include providing comprehensive health services to all the population, reinforcing specific preventive programs, improving certain basic health indicators and prompting intersectoral collaboration.

We present general comments on the epidemiology of measles considering the pre-vaccine era as well as the post-vaccine period in which some changes can be observed: the decrease in morbidity and mortality, the extension of the inter-epidemic interval, the increase in the mean age of infection, etc. We make some estimations about the vaccine coverage and the ideal age of immunization for the goal of eradication (assuming a lifelong immunity for the vaccinees). The technical problems in measles immunization are also revised explaining why no continental country has been able to eliminate the disease. We describe the epidemiological situation in North America, Mexico and Latin American countries. Lastly we present the Mexican experience with the inhaled aerosolised vaccine: the studies in Monterrey (Sabin et al, 1982), other investigation in Mexico, D.F. and in the State of Jalisco, as well as the mass campaigns in Aguascalientes in 1988 and in Coahuila and Nuevo León in 1989. We propose it as an effective, harmless, simple, inexpensive and practical method.

Comparison of the figures for measles morbidity in Mexico over the years is difficult because of the different rates of reporting of cases. In the 1960s, approximately 3% of the true number of cases of measles was reported, whereas in 1980 this percentage increased to approximately 20%. A more representative time curve can be drawn for mortality, which dropped sharply in 1973-1980 as a result of the extensive use of measles vaccine. The relationship between measles and immunization is close, and morbidity for the above period is a mathematical function of the number of doses of vaccine distributed. During 1981, about four million doses of vaccine were administered, and in 1982 another four million children will be immunized, with a coverage of 70% of the susceptible population. It is hoped that in 1982 the incidence of measles will decrease to the low levels obtained in 1974-1975, although eradication in the near future seems unlikely.

In 1959, oral poliovirus vaccine ( OPV ) was introduced as an antiepidemic measure in Mexico. As in many other developing countries, the vaccine was misused, coverages achieved were often poor, and an adequate cold chain was lacking. However, in 1972 a mass campaign reached 70% of children younger than five years of age, and consequently the reported cases declined sharply from 1.9 to 0.4 per 100,000 population. Due to economic restrictions, only single doses of monovalent type 1 OPV were administered to 80% of the target population in 1981, 1982, and 1983. The present incidence of poliomyelitis of 0.1 per 100,000 population represents a 96.7% reduction from the rate during the prevaccine era, when the annual average rate was 4.26 per 100,000. The present aim of poliomyelitis control is to maintain and decrease the present incidence of disease. Future plans are to continue mass vaccination in an attempt to reach small and isolated villages that have been without vaccination and limit possible rural foci of wild poliovirus.

A binational investigation was conducted in two Mexican cities in 1980 to study epidemiologic characteristics of dengue. Two study areas were selected in each of the cities (Merida and Tampico); in each area, in February and in September, sanitarians recorded information concerning abundance of Aedes aegypti, and public health nurses obtained blood specimens and clinical information from residents. Ninety-nine individuals (24% of the study population) showed serologic evidence of recent dengue 1 infection by hemagglutination inhibition or complement fixation. Infection rates in the four study areas (9%-51%) increased with age in three of the four areas and were higher in females in all four areas. These differences in rates may be related to exposure to infectious mosquitoes in the home; A. aegypti feed most actively during daylight hours, and both females (p less than 0.001) and older individuals (p less than 0.001) were more likely than males or younger persons to be in the home when the study was conducted. A positive correlation was found between infection rates and the container index (number of potential A. aegypti breeding sites per premise--Pearson correlation coefficient 0.95, p = 0.05), suggesting that this index may be a useful predictor of neighborhoods at high risk of dengue transmission. Pending additional studies, public cleanup campaigns should be targeted to neighborhoods in which container indices are highest when an outbreak of dengue is likely to occur.