IMMUNIZATION BY INHALATION OF AEROSOLIZED MEASLES-VACCINE

The importance of effectively protecting infants against measles in substantial because of the number of lives that can be saved and the morbidity that can be prevented. (i) Infants contract measles before the recommended age of immunization. (ii) Circulating maternal antibodies render measles vaccination ineffective in many infants. These problems have led to clinical trials of immunizing infants using routes other than the usual subcutaneous one. One promising approach is the inhalation of aerosolized vaccine. This study was undertaken to try to immunize very young infants using easily accessible vaccine and ordinary equipment. Infants aged 4-6 months were selected for measles immunization by inhalation. They were clinically well, with no history of tuberculosis or asthma. From each child, 0.2 ml of blood was obtained by finger-prick. The blood was kept on ice, then centrifuged and the serum stored in a freezer at -20°C. Each child was weighed and clinically assessed and his rectal temperature recorded. Using a plastic nebulizer to hold reconsituted vaccine by SCLAVO® of Italy and an ordinary foot pump, the vaccine was aerosolized. One thousand TCID50 of the vaccine was administered to each child with a vinyl face mask for a period of at least 30 s, to allow him to retain 250 TCID50. The child was then clinically followed up three times a week for 4 weeks with particular reference to (i) fever, (ii) conjunctivitis, (iii) cough, and (iv) skin rash. None of the infants developed any of the above signs during the interval. At the end of 6 weeks, another 0.1 ml of blood was obtained from each child by finger-pricks. All the infants had persistent maternal antibodies at the time of immunization, but 86% nevertheless seroconverted, and none of the infants developed measles up to the age of 1 year. This study demonstrated the effectiveness of aerosol delivery of measles vaccine to very young infants, using a readily available measles vaccine and simple equipment, such as the foot pump, which did not require electricity.