Background

Measles, mumps, rubella, and varicella are 4 common childhood diseases caused by measles virus, mumps virus, rubella virus, and varicella virus, respectively. These diseases may ba associated with serious complications and/or death. For example, measles can be associated with pneumonia and encephalitis; mumps can be associated with aseptic meningitis, deafness, and orchitis; rubella occurring during pregnancy can cause congenital rubella syndrome in the infants of infected mothers; and wild-type varicella can be associated with bacterial superinfection, pneumonia, encephalitis, and Reye's syndrome.

Mechanism of action

In clinical efficacy studies, seroconversion in response to vaccination against measles, mumps, and rubella paralleled protection from these diseases. Also, in previous studies with varicella vaccine, antibody responses against varicella virus ≥ 5 units/mL in a glycoprotein enzyme-linked immunosorbent assay (gpELISA) (not commercially available) similarly correlated with long-term protection. Clinical studies with a single dose of ProQuad have shown that vaccination elicited rates of antibody responses against measles, mumps, and rubella that were similar to those observed after vaccination with a single dose of M-M-R II (see Clinical Studies) and seroresponse rates for varicella virus were similar to those observed after vaccination with a single dose of VARIVAX® (see Clinical Studies). The duration of protection from measles, mumps, rubella, and varicella infections after vaccination with ProQuad is unknown.

Persistence of Antibody Responses after Vaccination

The persistence of antibody at 1 year after vaccination was evaluated in a subset of 2107 children enrolled in the clinical trials. Antibody was detected in 98.9% (1722/1741) for measles, 96.7% (1676/1733) for mumps, 99.6% (1796/1804) for rubella, and 97.5% (1512/1550) for varicella ( ≥ 5 gpELISA units/mL) of vaccinees following a single dose of ProQuad.

Experience with M-M-R II demonstrates that antibodies to measles, mumps, and rubella viruses are still detectable in most individuals 11 to 13 years after primary vaccination.¹ Varicella antibodies were present for up to ten years post-vaccination in most of the individuals tested who received 1 dose of VARIVAX.

Clinical Studies

Formal studies to evaluate the clinical efficacy of ProQuad have not been performed.

Efficacy of the measles, mumps, rubella and varicella components of ProQuad was previously established in a series of clinical studies with the monovalent vaccines. A high degree of protection from infection was demonstrated in these studies.^2-9

Immunogenicity

Immunogenicity was studied in 5835 healthy children 12 months to 6 years of age with a negative clinical history of measles, mumps, rubella, and varicella who participated in 5 randomized clinical trials. The immunogenicity of ProQuad was similar to that of its individual component vaccines (M-M-R II and VARIVAX), which are currently used in routine immunization.

The presence of detectable antibody was assessed by an appropriately sensitive enzyme-linked immunosorbent assay (ELISA) for measles, mumps (wild-type and vaccine-type strains), and rubella, and by gpELISA for varicella. For evaluation of vaccine response rates, a positive result in the measles ELISA corresponded to measles antibody concentrations of > 255 mlU/mL when compared to the WHO II (66/202) Reference Immunoglobulin for Measles.

Children were positive for mumps antibody if the antibody level was ≥ 10 ELISA units/mL. A positive result in the rubella ELISA corresponded to concentrations of ≥ 10 IU rubella antibody/mL when compared to the WHO International Reference Serum for Rubella; children with varicella antibody levels ≥ 5 gpELISA units/mL were considered to be seropositive since a response rate based on ≥ 5 gpELISA units/mL has been shown to be highly correlated with long-term protection.

Children who received a single dose of ProQuad at 12-23 months of age

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