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CLINICAL PHARMACOLOGY

Measles is a common childhood disease, caused by measles virus (paramyxovirus), that may be associated with serious complications and/or death. For example, pneumonia and encephalitis are caused by measles.

The impact of measles vaccination on the natural history of each disease in the United States can be quantified by comparing the maximum number of measles cases reported in a given year prior to vaccine use to the number of cases of each disease reported in 1995. A total of 894,134 cases reported in 1941 compared to 288 cases reported in 1995 resulted in a 99.97% decrease in reported cases of measles.1

Extensive clinical trials have demonstrated that ATTENUVAX (measles virus vaccine live) is highly immunogenic and generally well tolerated.2-6 A single injection of the vaccine has been shown to induce measles hemagglutination-inhibition (HI) antibodies in 97% or more of susceptible persons. However, a small percentage (1-5%) of vaccinees may fail to seroconvert after the primary dose (see also INDICATIONS AND USAGE, Recommended Vaccination Schedule).

A study7 of 6 month old and 15 month old infants born to vaccine-immunized mothers demonstrated that, following vaccination with ATTENUVAX (measles virus vaccine live) , 74% of the 6 month old infants developed detectable neutralizing antibody (NT) titers while 100% of the 15 month old infants developed NT. This rate of seroconversion is higher than that previously reported for 6 month old infants born to naturally immune mothers tested by HI assay. When the 6 month old infants of immunized mothers were revaccinated at 15 months, they developed antibody titers equivalent to the 15 month old vaccinees. The lower seroconversion rate in 6 month olds has two possible explanations: 1) Due to the limit of the detection level of the assays (NT and enzyme immunoassay [EIA]), the presence of trace amounts of undetectable maternal antibody might interfere with the seroconversion of infants; or 2) The immune system of 6 month olds is not always capable of mounting a response to measles vaccine as measured by the two antibody assays.

There is some evidence to suggest that infants who are born to mothers who had natural measles and who are vaccinated at less than one year of age may not develop sustained antibody levels when later revaccinated. The advantage of early protection must be weighed against the chance for failure to respond adequately on reimmunization.8,9

Efficacy of measles vaccine was established in a series of double-blind controlled field trials which demonstrated a high degree of protective efficacy.2,10,11 These studies also established that seroconversion in response to measles vaccination paralleled protection from these diseases.12

Following vaccination, antibodies associated with protection can be measured by neutralization assays, HI, or ELISA (enzyme linked immunosorbent assay) tests. Neutralizing and ELISA antibodies to measles virus are still detectable in most individuals 11-13 years after primary vaccination.10,13

REFERENCES

1. Monthly Immunization Table, MMWR 45(1): 24-25, January 12, 1996.

2. Hilleman, M.R.; Buynak, E.B.; Weibel, R.E.; et al: Development and Evaluation of the Moraten Measles Virus Vaccine, JAMA 206(3): 587-590, 1968.

3. Swartz, T.; Klingberg, W.; Nishmi, M.; Goldblum, N.; Gerichter, C.; Yofe, Y.; Cockburn, W.C.: A comparative study of four live measles vaccines in Israel, Bull. WHO 39: 285-292, 1968.

4. Krugman, S.; Constantinides, P.; Medovy, H.; Giles, J.P.: Comparison of two further attenuated live measles-virus vaccines, Amer. J. Dis. Child. 117: 137-138, Feb. 1969.

5. Studies conducted under the direction of Dr. Conrado Ristori, National Health Service, Santiago, Chile (Unpublished Data).

6. Studies conducted under the direction of Dr. Victor Villarejos, Louisiana State University International Center of Medical Research and Training, San Jose, Costa Rica (Unpublished Data).

7. Johnson, C.E.; et al: Measles Vaccine Immunogenicity in 6- Versus 15-Month-Old Infants Born to Mothers in the Measles Vaccine Era, Pediatrics, 93(6): 939-943, 1994.

8. Linneman, C.C.; et al: Measles Immunity After Vaccination: Results in Children Vaccinated Before 10 Months of Age, Pediatrics, 69(3): 332-335, March 1982.

9. Stetler, H.C.; et al: Impact of Revaccinating Children Who Initially Received Measles Vaccine Before

10. Months of Age, Pediatrics 77(4): 471-476, April 1986. 10. Unpublished data: Files of Merck Research Laboratories.

11. Cutts, F.T.; Henderson, R.H.; Clements, C.J.; et al: Principles of measles control, Bull WHO 69(1): 1-7, 1991.

12. Rosen, L.: Hemagglutination and Hemagglutination-Inhibition with Measles Virus, Virology13: 139-141, January 1961.

13. Watson, J.C.; Pearson, J.A.; Erdman, D.D.; et al: An Evaluation of Measles Revaccination Among School-Entry Age Children, 31st Interscience Conference on Antimicrobial Agents and Chemotherapy, Abstract #268, 143, 1991.

Last reviewed on RxList: 12/2/2008
This monograph has been modified to include the generic and brand name in many instances.

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