Source: Health Products Regulatory Authority (ZA) Revision Year: 2020 Publisher: MSD (Pty) Ltd, 117 16 th Road, Halfway House, 1685, South Africa
A.30.1 Antibodies
OMZYTA is a sterile lyophilised preparation of (1) ATTENUVAX* (Measles Virus Vaccine Live, MSD), a more attenuated line of measles virus, derived from Enders' attenuated Edmonston strain and propagated in chick embryo cell culture; (2) MUMPSVAX* (Mumps Virus Vaccine Live, MSD), the Jeryl Lynn (B level) strain of mumps virus propagated in chick embryo cell culture; and (3) MERUVAX* II (Rubella Virus Vaccine Live, MSD), the Wistar RA 27/3 strain of live attenuated rubella virus propagated in WI 38 human diploid lung fibroblasts.
Clinical studies of 284 triple seronegative children, 11 months to 7 years of age, demonstrated that OMZYTA is highly immunogenic and generally well tolerated. In these studies, a single injection of the vaccine induced measles hemagglutination inhibition (HI) antibodies in 95%, mumps neutralising antibodies in 96% and rubella HI antibodies in 99% of susceptible persons. However, a small percentage (1 to 5%) of vaccinees may fail to seroconvert after the primary dose.
A study of 6-month-old and 15-month-old infants born to vaccine-immunised mothers demonstrated that, following vaccination with ATTENUVAX, 74% of the 6-month-old infants developed detectable neutralising antibody (NT) titres while 100% of the 15-month-old infants developed NT. This rate of seroconversion is higher than that previously reported for 6-monthold infants born to naturally immune mothers tested by HI assay. When the 6-month-old infants of immunised mothers were revaccinated at 15 months, they developed antibody titres 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.
Efficacy of measles, mumps and rubella vaccines was established in a series of double-blind controlled field trials which demonstrated a high degree of protective efficacy afforded by the individual vaccine components. These studies also established that seroconversion in response to vaccination against measles, mumps and rubella paralleled protection from these diseases.
Following vaccination, antibodies associated with protection can be measured by neutralisation assays, HI or ELISA (enzyme linked immunosorbent assay) tests. Neutralising and ELISA antibodies to measles, mumps and rubella viruses are still detectable in most individuals 11 to 13 years after primary vaccination.
Not applicable.
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