The decline of measles antibody titers in previously vaccinated adults: a cross-sectional analysis.

The global reemergence of measles in 2018-2019 reinforces the relevance of high-coverage immunization to maintain the disease elimination. During an outbreak in the Sao Paulo State in 2019, several measles cases were reported in individuals who were adequately vaccinated according to the current immunization schedule recommends. This study aimed to assess measles IgG antibody seropositivity and titers in previously vaccinated adults. A cross-sectional study was conducted at CRIE-HC-FMUSP (Sao Paulo, Brazil) in 2019. It included healthy adults who had received two or more Measles-Mumps-Rubella vaccines (MMR) and excluded individuals with immunocompromising conditions. Measles IgG antibodies were measured and compared by ELISA (Euroimmun®) and chemiluminescence (LIASON®). The association of seropositivity and titers with variables of interest (age, sex, profession, previous measles, number of measles-containing vaccine doses, interval between MMR doses, and time elapsed since the last MMR dose) was analyzed. A total of 162 participants were evaluated, predominantly young (median age 30 years), women (69.8%) and healthcare professionals (61.7%). The median interval between MMR doses was 13.2 years, and the median time since the last dose was 10.4 years. The seropositivity rate was 32.7% by ELISA and 75.3% by CLIA, and a strong positive correlation was found between the tests. Multivariate analyses revealed that age and time since the last dose were independently associated with positivity. Despite being a single-center evaluation, our results suggest that measles seropositivity may be lower than expected in adequately immunized adults. Seropositivity was higher among older individuals and those with a shorter time since the last MMR vaccine dose.

The decline of measles antibody titers in previously vaccinated adults: a cross-sectional analysis

ABSTRACT The global reemergence of measles in 2018-2019 reinforces the relevance of high-coverage immunization to maintain the disease elimination. During an outbreak in the Sao Paulo State in 2019, several measles cases were reported in individuals who were adequately vaccinated according to the current immunization schedule recommends. This study aimed to assess measles IgG antibody seropositivity and titers in previously vaccinated adults. A cross-sectional study was conducted at CRIE-HC-FMUSP (Sao Paulo, Brazil) in 2019. It included healthy adults who had received two or more Measles-Mumps-Rubella vaccines (MMR) and excluded individuals with immunocompromising conditions. Measles IgG antibodies were measured and compared by ELISA (Euroimmun®) and chemiluminescence (LIASON®). The association of seropositivity and titers with variables of interest (age, sex, profession, previous measles, number of measles-containing vaccine doses, interval between MMR doses, and time elapsed since the last MMR dose) was analyzed. A total of 162 participants were evaluated, predominantly young (median age 30 years), women (69.8%) and healthcare professionals (61.7%). The median interval between MMR doses was 13.2 years, and the median time since the last dose was 10.4 years. The seropositivity rate was 32.7% by ELISA and 75.3% by CLIA, and a strong positive correlation was found between the tests. Multivariate analyses revealed that age and time since the last dose were independently associated with positivity. Despite being a single-center evaluation, our results suggest that measles seropositivity may be lower than expected in adequately immunized adults. Seropositivity was higher among older individuals and those with a shorter time since the last MMR vaccine dose.

Evaluation of the Panbio COVID-19 Antigen Rapid Diagnostic Test in Subjects Infected with Omicron Using Different Specimens.

Community testing is a crucial tool for the early identification of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and transmission control. The emergence of the highly mutated Omicron variant (B.1.1.529) raised concerns about its primary site of replication, impacting sample collection and its detectability by rapid antigen tests. We tested the performance of the Panbio antigen rapid diagnostic test (Ag-RDT) using nasal and oral specimens for COVID-19 diagnosis in 192 symptomatic individuals, with quantitative reverse transcription-PCR (RT-qPCR) of nasopharyngeal samples as a control. Variant of concern (VOC) investigation was performed with the 4Plex SARS-CoV-2 screening kit. The SARS-CoV-2 positivity rate was 66.2%, with 99% of the positive samples showing an amplification profile consistent with that of the Omicron variant. Nasal Ag-RDT showed higher sensitivity (89%) than oral (12.6%) Ag-RDT. Our data showed good performance of the Ag-RDT in a pandemic scenario dominated by the Omicron VOC. Furthermore, our data also demonstrated that the Panbio COVID-19 antigen rapid diagnostic test does not provide good sensitivity with oral swabs for Omicron Ag-RDT detection. IMPORTANCE This study showed that the antigen rapid test for COVID19 worked fine using nasal swabs when it was utilized in patients infected with the Omicron variant, showing a concordance with PCR in 93% of patients tested. The nasal swab yielded more reliable results than the oral swab when an antigen rapid diagnosis test (the Panbio COVID-19 antigen rapid diagnostic test) was used in patients infected with the Omicron variant.

Prolonged SARS-CoV-2 Positivity in Immunocompetent Patients: Virus Isolation, Genomic Integrity, and Transmission Risk.

Current guidelines for patient isolation in COVID-19 cases recommend a symptom-based approach, averting the use of control real-time reverse transcription PCR (rRT-PCR) testing. However, we hypothesized that patients with persistently positive results by RT-PCR for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) could be potentially infectious for a prolonged time, even if immunocompetent and asymptomatic, which would demand a longer social isolation period than presently recommended. To test this hypothesis, 72 samples from 51 mildly symptomatic immunocompetent patients with long-lasting positive rRT-PCR results for SARS-CoV-2 were tested for their infectiousness in cell culture. The serological response of samples from those patients and virus genomic integrity were also analyzed. Infectious viruses were successfully isolated from 34.38% (22/64) of nasopharynx samples obtained 14 days or longer after symptom onset. Indeed, we observed successful virus isolation up to 128 days. Complete SARS-COV-2 genome integrity was demonstrated, suggesting the presence of replication-competent viruses. No correlation was found between the isolation of infectious viruses and rRT-PCR cycle threshold values or the humoral immune response. These findings call attention to the need to review current isolation guidelines, particularly in scenarios involving high-risk individuals. IMPORTANCE In this study, we evaluated mildly symptomatic immunocompetent patients with long-lasting positive rRT-PCR results for SARS-CoV-2. Infectious viruses were successfully isolated in cell cultures from nasopharynx samples obtained 14 days or longer after symptom onset. Indeed, we observed successful virus isolation for up to 128 days. Moreover, SARS-CoV-2 genome integrity was demonstrated by sequencing, suggesting the presence of replication-competent viruses. These data point out the risk of continuous SARS-CoV-2 transmission from patients with prolonged detection of SARS-CoV-2 in the upper respiratory tract, which has important implications for current precaution guidelines, particularly in settings where vulnerable individuals may be exposed (e.g., nursing homes and hospitals).