Recommendations for UseIn view of the significant morbidity and mortality against measles the government is urged to take rapid steps such as surveillance for disease, improvement of primary coverage, supplementary immunization activities and better case management. As discussed earlier vaccine immunogenicity and efficacy are best when the vaccine is administered beyond the age of 12 months. However in India a significant proportion of measles cases occur below the age of 12 months. Hence in order to achieve the best balance between these competing demands of early protection and high seroconversion, completed 9 months of age has been recommended as the appropriate age for measles vaccination in India. In case of an outbreak, however, the vaccine can be given to infants as young as 6 months. Administration of the vaccine within 2 days of exposure protects and or modifies the severity of clinical disease. The vaccine should be given irrespective of prior history of measles as any exanthematous illness is often confused as measles. In view of the significant cases of primary vaccine failures with the first dose of the vaccine an additional dose of measles vaccine preferably as MMR vaccine at the age of 15 months is required for durable and possibly lifelong protection against measles. |
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A safe, effective and reasonably inexpensive vaccine is available against measles for the past 5 decades and measles is a potentially eradicable disease. Most developed and many developing countries have significantly reduced the burden and even eliminated measles by a multi pronged strategy comprising of improved routine coverage, provision of a second dose through routine immunization or periodic supplementary immunization activities, careful surveillance and appropriate case management.
Interestingly measles immunization saves more lives per unit cost than any other health intervention. However measles still kills around 6,00,000 children globally and 80,000 in India every year. Additionally, measles causes significant morbidity including malnutrition, blindness and neurologic damage. Suboptimal primary immunization coverage which in India as per National Family Health Survey-3 (NFHS-3) is only 60% is primarily responsible for this dismal scenario and needs to be urgently addressed. Vaccine
All currently used measles vaccines are live attenuated vaccines. Most of the currently used live attenuated measles vaccine strains originate from the original Edmonston strain and include Schwarz, Edmonston Zagreb, Moraten and Edmonston- B strains. Indian vaccines are usually formulated from the Edmonston Zagreb strain grown on human diploid cells or purified chick embryo cells. Each dose contains at least 1000 infective units and has no preservative.
It is supplied freeze-dried in single dose or multidose vials with distilled water as a diluent. The vaccine may be stored frozen or at 2 to 8°C (shelf life 2 years). Reconstituted vaccine is destroyed by light and is very heat labile (loses 50% potency at 20° C and 100% at 37° C after 1 hour) and is susceptible to contamination as it does not have any preservative. For these reasons reconstituted vaccine should be protected from light, kept at 2 to 8° C and used within 4-6 hours of reconstitution. This is particularly applicable to multidose vials. The dose is 0.5 ml subcutaneously or intramuscularly, preferably over the upper arm/anterolateral thigh.
Immunogenicity and efficacy depends on the age of administration due to interference by preexisting maternal antibodies. Seroconversion rates are around 60% at the age of 6 months, 80-85% at the age of 9 months and beyond 95% at the age of 12-15 months. While antibody titers wane over the years measles specific cellular immunity persists and provides lifelong protection. Secondary vaccine failures rarely occur.
Immunogenicity is lower in the immunocompromised including HIV. In HIV infected infants superior seroconversion rates are seen at 6 months as compared to 9 months due to progressive immunodeficiency with age. Vaccine efficacy studies from India have reported varying efficacies ranging from 60-80% when given at the age of 9 months.
Adverse reactions apart from local pain and tenderness include a mild measles like illness 7-12 days after vaccination in 2-5% of the vaccinees. Thrombocytopenic purpura may occur at a frequency of 1/30,000 vaccinees. Though depression of cell mediated immunity may occur, it recovers within 4 weeks and is considered harmless even for those with early HIV or latent/unrecognized tuberculosis. There is no data to support causal relationship between measles vaccine and encephalitis, GBS, subacute sclerosing encephalitis and autism. There is no transmission of the vaccine virus from the vaccinees to the contacts.
Measles vaccine has been the cause of several infant
deaths in India due to toxic shock syndrome and use of
succinylcholine instead of distilled water as the diluents. The
vaccine is contraindicated in the severely immunocompromised,
in those with history of severe allergic reactions to
the constituents and in pregnancy. The vaccine should be
administered to those with HIV infection irrespective of degree
of immunocompromise as here the benefits outweigh the risks.
The vaccine may be safely given to those with history of egg
allergy. The vaccine may be given along with all childhood
vaccines with the exception of BCG vaccine.