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Despite the availability of a highly efficacious vaccine, a global resurgence of measles infections has occurred, largely due to decreased vaccination coverage and waning immunity following the two-dose vaccination schedule. This study aims to assess the cellular immune response in individuals who did not respond to the two-dose MMR vaccine and evaluate the efficacy and durability of immune responses after booster doses. An observational study was conducted involving 24 individuals who were seronegative for measles years after completing the two-dose MMR vaccine schedule. Of these, 11 seroconverted after a single booster dose, while 13 required an additional booster. Antibody levels were monitored 1 and 3 years post-booster. Cellular immune responses were evaluated in 10 nonresponders by in vitro stimulation of PBMCs with UV-inactivated measles virus. In nonresponders, measles virus stimulation did not induce significant alterations in T, B, or NK cell populations, indicating a lack of measles-specific immune memory. However, stimulation with rubella induced a significant immune response. Booster doses in subjects with waning antibodies resulted in low IgG titers, which significantly declined over 3 years. Neutralizing antibody titers were also low for both double and single booster recipients. This study highlights the limited long-term efficacy of booster doses in individuals with waning immunity or nonresponsiveness to the measles vaccine. Current vaccination strategies relying on booster doses may not be sufficient for sustained protection in these individuals. Improving vaccine formulations to elicit stronger and longer-lasting immunity is essential for effective measles control and elimination., (© 2024 The Author(s). Journal of Medical Virology published by Wiley Periodicals LLC.)

Data regarding antibody responses to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) in patients infected with COVID-19 are not yet available. In this study, we aimed to evaluate serum antibody responses in patients regardless of the outcome. We measured the circulating immunoglobulin G (IgG) antibody levels in 60 subjects with a certified history of SARS-CoV-2 infection by using immunoenzymatic, chemiluminescent, and Neutralization assays. Half patients had a severe infection, the other half were pauci-symptomatic. We analyzed their antibody response to see the trend of the humoral response. Our results showed a significant difference in circulating IgG level among the two groups. The neutralizing antibody response against SARS-CoV-2 was significantly higher among those who had severe disease. Furthermore, ten subjects from each group were screened twice, and a declining antibody trend was observed in pauci-symptomatic individuals. These findings provide evidence that humoral immunity against SARS-CoV-2 in pauci-symptomatic people is weak and may not be long-lasting. This may have implications for immunity strategy and prevention, since it is still not clear whether a time-dependent decrease of both circulating and neutralizing antibodies to nonprotective levels could occur in a longer time span and whether potential vaccines are able to induce a herd immunity and a durable response., (© 2021 Wiley Periodicals LLC.)