What is the significance of positive antibody titers after Measles, Mumps, and Rubella (MMR) vaccination?

From the Guidelines

Positive titers after MMR vaccine are expected to develop in approximately 90%--95% of recipients within 2 weeks of the first dose, with the majority of non-responders developing immunity after a second dose. The development of positive titers after MMR vaccination is a critical aspect of assessing immunity against measles, mumps, and rubella. According to the recommendations of the Advisory Committee on Immunization Practices (ACIP) and the American Academy of Family Physicians (AAFP) 1, a single dose of the MMR vaccine induces protective antibody levels in about 90%--95% of recipients. However, a second dose is recommended to ensure that those who did not respond to the first dose have another opportunity to develop immunity.

Key Points to Consider

• The majority of individuals who fail to respond to the first dose of MMR vaccine will respond to a second dose 1.
• Factors such as age, immune status, and proper vaccine handling can influence the immune response to the MMR vaccine.
• Healthcare workers and individuals at high risk for exposure should confirm immunity through documentation of vaccination or positive titers.

Immune Response to MMR Vaccine

The MMR vaccine contains live attenuated viruses, which replicate in the body and stimulate both humoral and cell-mediated immunity without causing disease. This robust immune response is responsible for the high efficacy of the vaccine in preventing measles, mumps, and rubella. While some individuals may not develop positive titers after vaccination, they may still have adequate cellular immunity to protect against disease.

Clinical Implications

In clinical practice, the development of positive titers after MMR vaccination is an important indicator of immunity. However, it is essential to consider the individual's overall immune status and risk factors for exposure when interpreting titers. If titers are negative or equivocal after completing the recommended two-dose series, an additional dose may be administered rather than rechecking titers, as some individuals may have adequate cellular immunity despite low antibody levels.

From the Research

Positive Titers after MMR Vaccine

• The MMR vaccine has been shown to induce long-term immunity against measles, mumps, and rubella viruses in healthy young children, with antibody titers remaining above the seropositivity threshold after 10 years 2.
• A second dose of MMR vaccine given later in life has a minor and transient effect on anti-measles and anti-rubella waning titers, but has a boosting effect on anti-mumps antibody titers and seropositivity rates 2.
• In adult hematopoietic cell transplant recipients, one dose of MMR vaccine elicited protective titers in the majority of patients, and a second vaccine dose was immunogenic in nonresponders 3.
• The immunogenicity and safety of a measles and rubella-containing vaccine administered at age 6 and 9 months in Bangladesh have been assessed, with results showing that a first dose of MR vaccine at 6 months induced seroconversion in 94% of infants for both measles and rubella, and a second dose at 9 months boosted seroconversion to 99% 4.
• Detection of serum antibodies against measles, mumps, and rubella after primary MMR vaccination in children has shown that IgG and IgM antibody levels were below the assay cut-off levels against measles and rubella in approximately one-fourth of the children, suggesting that a second dose may be necessary to raise the level of protection 5.

Factors Affecting Positive Titers

• The type of MMR vaccine used, such as Priorix or Priorix-Tetra, can affect the level of antibody titers induced, with Priorix-Tetra eliciting higher anti-measles antibody titers 2.
• The timing of the second dose of MMR vaccine, whether given later in life or at a standard interval, can affect the boosting effect on antibody titers 2, 3.
• Individual factors, such as age and immune status, can affect the response to MMR vaccination, with some individuals requiring a second dose to achieve protective titers 3, 5.

Immune Response

• The immune response to MMR vaccination involves the production of IgG and IgM antibodies, which can be measured by enzyme-linked immunoassay (ELISA) 2, 5.
• The frequency of antigen-specific memory B cells can be associated with antibody titers, suggesting a role for cellular immunity in maintaining long-term protection 6.
• The effect of MMR vaccination on immune responses, such as antibody avidity and neutralizing antibody titers, can vary depending on the individual and the vaccine used 6, 4.