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Mumps outbreaks continue to occur worldwide despite widespread vaccination efforts. A notable outbreak in the United States in 2006 led to thousands of confirmed or probable mumps cases, with a high incidence among college students aged 18-24. It is unclear whether these outbreaks in vaccinated individuals result from primary vaccine failure or waning immunity.
Understanding Vaccine Efficacy
Studies have shown varying rates of seroconversion after mumps vaccination. Although some studies report high rates (over 90%), efficacy studies indicate lower rates, starting at 64% after a single vaccine dose and rising to 88% after two doses. It is important to consider that measuring only mumps-specific IgG levels may overestimate vaccine efficacy. One study found low levels of specific neutralizing antibodies in patients who received one dose of the vaccine but still contracted mumps disease. These findings align with similar observations in measles vaccine studies, suggesting that some individuals may not respond adequately to the initial immunization but may respond to a second dose.
Primary Vaccine Failure and Waning Immunity
Primary vaccine failure plays a significant role in disease susceptibility, but the involvement of waning immunity and subsequent secondary vaccine failure remains unclear. Some studies have examined mumps antibody avidity assays in vaccinated individuals who contracted mumps disease. These studies revealed high avidity titers associated with a recall response to the antigen rather than a primary response. However, such studies have primarily focused on populations where only one vaccine dose was administered, and more research is needed in populations following the recommended two-dose schedule.
Factors Influencing Immunogenicity
The effectiveness of the mumps vaccine relies on the generation of mumps-specific antibodies, particularly neutralizing antibodies, and the development of cell-mediated immunity. Antigenic differences between circulating wild-type viruses and vaccine strains have been speculated to contribute to mumps outbreaks. Global variations in mumps vaccine strains suggest that some strains may not be fully neutralized by vaccine-induced immunity, potentially leaving highly vaccinated populations susceptible to infection.
The Role of Cell-Mediated Immunity
While the significance of cell-mediated immunity in mumps virus protection is not fully understood, evidence suggests that T lymphocytes play a crucial role in recovery from acute viral infections and long-term disease protection. Individuals lacking humoral immunity still exhibit protection against infection or severe disease, as demonstrated in studies on measles virus. Animal studies also highlight the limited role of humoral immunity and the greater importance of cell-mediated immunity in controlling measles virus replication. Similar patterns of immunity are expected for mumps virus due to its classification in the same viral family as measles.
Investigating Long-Term Immunity
To assess the persistence of mumps immunity years after vaccination, this study investigated cellular and humoral immunity in adults who had received two doses of mumps-containing vaccines during childhood. A control group consisted of adults with a history of mumps virus infection during childhood. The focus was on evaluating cell-mediated immunity, particularly the response of memory CD4+ T cells to mumps antigen exposure. This study employed flow cytometry to evaluate mumps-specific CD4+ T cells and their single-cell expression of interferon (IFN)-γ in response to mumps antigen stimulation.
In summary, understanding the type of immunity resulting from recovering from mumps is crucial for optimizing vaccination strategies and controlling outbreaks. 5 WS is committed to providing reliable and up-to-date information on various topics, including immunity and infectious diseases. Visit 5 WS for more valuable insights.