Measles outbreak in Gothenburg urban area, Sweden, 2017 to 2018: low viral load in breakthrough infections

Measles outbreak associated with a preschool setting among partially vaccinated children in the Tel Aviv District, Israel, October 2023

In October 2023, the Tel Aviv District was notified of ten cases of measles. The outbreak initiated in a preschool with high vaccination coverage with one dose of MMR vaccine. Serological testing was available for eight patients (six children and two adults). Among the six children vaccinated with one dose of MMR vaccine, primary vaccine failure was demonstrated. Among the adults, secondary vaccine failure was confirmed. The outbreak was successfully contained due to a combination of factors, notably its occurrence within a population characterized by high vaccination coverage in Tel Aviv, during a period of restricted public interactions due to the prevailing state of war in the country. Despite challenging wartime conditions, effective prophylactic measures were promptly executed, encompassing a 2-dose MMR vaccination schedule for close contacts and the broader community of children in the TA district, successfully curbing the outbreak and preventing widespread infections.

Adapting response to a measles outbreak in a context of high vaccination and breakthrough cases: an example from Vaud, Switzerland, January to March 2024

A measles outbreak with 51 cases occurred in the canton of Vaud, Switzerland, between January and March 2024. The outbreak was triggered by an imported case, and 37 (72.5%) subsequent cases were previously vaccinated individuals. Epidemiological investigations showed that vaccinated measles cases were symptomatic and infectious. In a highly vaccinated population, it is important to raise awareness among healthcare professionals to suspect and test for measles virus when an outbreak is declared, irrespective of the vaccination status of the patients.

Measles in Czech population with varying vaccination rates in 2018-2019: clinical and laboratory differences between vaccinated and unvaccinated individuals and their relevance to clinical practice

BACKGROUND AND OBJECTIVES

In a highly vaccinated population, an increasing number of previously vaccinated measles cases can be expected. The aim of this study was to assess the effect of vaccination on the clinical course and immune response in relation to the current measles case definition.

METHODS

The presence of fever, catarrhal symptoms, exanthema and complications, and specific IgM and IgG positivity were assessed in all 230 patients and compared in 193 patients with known vaccination status, divided into measles-containing vaccine (MCV) groups: MCV0 (85 patients), MCV1 (25 patients) and MCV2 (83 patients).

RESULTS

Statistically significant differences between groups were found for catarrhal symptoms.Conjunctivitis and rhinitis were significantly less frequent in the MCV2 group (47% and 54%) compared to MCV0 (80% and 80%), p < 0.001 and p = 0.002 respectively. Typical exanthema was present in 74 (87%) MCV0 and 56 (67%) MCV2 patients, p = 0.005. Complications were most common in the MCV0 group (29%). ECDC clinical case criteria were met in 81 (95%) MCV0, 18 (72%) MCV1 and 59 (71%) MCV2 patients, p < 0.001. IgM were positive in 64 (83%) MCV0, 14 (74%) MCV1 and 36 (67%) MCV2 patients, differences were not statistically significant. There were highly significant differences in IgG between MCV0 and both vaccinated groups (p < 0.001).

CONCLUSIONS

A redefinition of the clinical case classification is essential to better capture modified measles and to raise awareness among healthcare workers of the differences in measles in vaccinated patients.

Measles Outbreak Response Activity in Japan, and a Discussion for a Possible Strategy of Outbreak Response Using Cycle Threshold Values of Real-Time Reverse Transcription PCR for Measles Virus in Measles Elimination Settings

Measles is a highly contagious, but vaccine-preventable disease caused by the measles virus (MeV). Although the administration of two doses of measles vaccines is the most effective strategy to prevent and eliminate measles, MeV continues to spread worldwide, even in 2022. In measles-eliminated countries, preparedness and response to measles outbreaks originating from imported cases are required to maintain elimination status. Under these circumstances, real-time reverse transcription (RT) PCR for MeV could provide a diagnostic method capable of strengthening the subnational capacity for outbreak responses. Real-time RT-PCR can detect MeV RNA from patients with measles at the initial symptomatic stage, which can enable rapid public health responses aimed at detecting their contacts and common sources of infection. Furthermore, low cycle threshold (Ct) values (i.e., high viral load) of throat swabs indicate high infectiousness in patients with measles. The high basic reproduction number of measles suggests that patients with high infectiousness can easily become super-spreaders. This opinion proposes a possible strategy of rapid and intensive responses to counter measles outbreaks caused by super-spreader candidates showing low Ct values in throat swabs. Our strategy would make it possible to effectively prevent further measles transmission, thereby leading to the early termination of measles outbreaks.

SARS-CoV-2 epitopes inform future vaccination strategies

All currently approved COVID-19 vaccines utilize the spike protein as their immunogen. SARS-CoV-2 variants of concern (VOCs) contain mutations in the spike protein, enabling them to escape infection- and vaccination-induced immune responses to cause reinfection. New vaccines are hence being researched intensively. Studying SARS-CoV-2 epitopes is essential for vaccine design, as identifying targets of broadly neutralizing antibody responses and immunodominant T-cell epitopes reveal candidates for inclusion in next-generation COVID-19 vaccines. We summarize the major studies which have reported on SARS-CoV-2 antibody and T-cell epitopes thus far. These results suggest that a future of pan-coronavirus vaccines, which not only protect against SARS-CoV-2 but numerous other coronaviruses, may be possible. The T-cell epitopes of SARS-CoV-2 have gotten less attention than neutralizing antibody epitopes but may provide new strategies to control SARS-CoV-2 infection. T-cells target many SARS-CoV-2 antigens other than spike, recognizing numerous epitopes within these antigens, thereby limiting the chance of immune escape by VOCs that mainly possess spike protein mutations. Therefore, augmenting vaccination-induced T-cell responses against SARS-CoV-2 may provide adequate protection despite broad antibody escape by VOCs.

Breakthrough Infections: A Challenge towards Measles Elimination?

Measles is one of the most contagious diseases known to man. Despite the existence of a safe and effective live attenuated vaccine, measles can appear in vaccinated individuals. Paradoxically, breakthrough cases increase as vaccination coverage in the general population rises. In measles endemic areas, breakthrough cases represent less than 10% of total infections, while in areas with high vaccination coverage these are over 10% of the total. Two different vaccination failures have been described: primary vaccination failure, which consists in the complete absence of humoral response and occurs in around 5% of vaccinated individuals; and secondary vaccination failure is due to waning immunity or incomplete immunity and occurs in 2–10% of vaccinees. Vaccination failures are generally associated with lower viral loads and milder disease (modified measles) since vaccination limits the risk of complicated disease. Vaccination failure seems to occur between six and twenty-six years after the last vaccine dose administration. This review summarizes the literature about clinical, serological, epidemiological, and molecular characteristics of measles breakthrough cases and their contribution to virus transmission. In view of the measles elimination goal, the assessment of the potential decline in antibody protection and the targeted implementation of catch-up vaccination are essential.

Diagnostic Significance of Lactate Dehydrogenase in Measles Virus Reinfection Cases

Lactate dehydrogenase (LDH) levels in measles virus (MeV) reinfection cases for the diagnosis of measles have not been extensively studied. Thus, we evaluated the significance of serum LDH in the immune response of patients with MeV reinfection in comparison with those of patients with primary infection. Among 70 patients who tested positive for MeV-RNA, 42 with high MeV-specific IgG avidity (HA) were suspected as cases of reinfection and 28 with low MeV-specific IgG (LA) were suspected as cases of primary infection. The viral loads in the HA group were also lower than those in the LA group (p < 0.001). The titers of MeV-specific IgM and IgG in the HA group were significantly lower and higher, respectively, than those in the LA group (p < 0.001). The total LDH and LDH isozyme levels were elevated in the LA group compared with those in the HA group (p < 0.001). Through receiver operating characteristic curve analyses, we determined that the area under the curve of total LDH level was 0.87 (95% confidence interval 0.74-1.00) and that the discriminatory accuracy was high for total LDH and all isozymes. By stepwise binary logistic regression analysis considering MeV-specific IgG avidity, we developed a model using IgG, IgM, and total LDH as explanatory variables, which was optimal for distinguishing the LA and HA groups (adjusted R² : 0.773, p < 0.001). Thus, the serum LDH level in addition to IgM and IgG may be useful parameters for differentiating MeV reinfection from primary infection. This article is protected by copyright. All rights reserved.

Immunogenicity after outbreak response immunization activities among young healthcare workers with secondary vaccine failure during the measles epidemic in Korea, 2019

BACKGROUND

Despite high vaccination coverage, measles outbreaks have been reported in measles elimination countries, especially among healthcare workers in their 20 and 30 s. This study was designed to identify measles-susceptible individuals and to evaluate whether primary or secondary vaccine failure occurred during measles outbreak response immunization (ORI) activities.

METHODS

The study population was divided into three groups as follows: natural immunity group (Group 1), vaccine-induced immunity group (Group 2), and vaccine failure group (Group 3). We evaluated the immunogenicity of measles among healthcare workers using three methods-enzyme-linked immunoassays, plaque reduction neutralization tests, and avidity assays. The results were assessed at baseline, 4 weeks after, and 6 months after the completion of measles-mumps-rubella (MMR) vaccination.

RESULTS

In total, 120 subjects were enrolled, with 40 subjects in each group. The median age of Group 3 was 29 years, which was significantly lower than that of the other groups. The baseline negative measles virus (MeV) IgG in Group 3 increased to a median value of 165 AU/mL at 4 weeks after ORI and was lower than that in Groups 1 and 2. The median neutralizing antibody titer was highest in Group 1, and this was significantly different from that in Group 2 or Group 3 at 4 weeks (944 vs. 405 vs. 482 mIU/mL, P = 0.001) and 6 months (826 vs. 401 vs. 470, P = 0.011) after ORI. The rates of high MeV avidity IgG were highest in Group 2, and these were significantly different from those in Groups 1 or 3 at 4 weeks (77.5 vs. 90% vs. 88.6%, P = 0.03) and 6 months (81 vs. 94.8 vs. 82.1%, P = 0.01) after ORI.

CONCLUSIONS

Considering the MeV-neutralizing antibodies and IgG avidity after MMR vaccination in measles-susceptible group, vaccine failure is inferred as secondary vaccine failure, and further data regarding the maintenance of immunogenicity are needed based on long-term data. The MeV-neutralizing antibody levels were highest in the natural immunity group, and the primary vaccine-induced immunity group showed the highest rates of high MeV IgG avidity.

Characterization of Vaccine Breakthrough Cases during Measles Outbreaks in Milan and Surrounding Areas, Italy, 2017–2021

Despite the existence of an effective live-attenuated vaccine, measles can appear in vaccinated individuals. We investigated breakthrough measles cases identified during our surveillance activities within the measles/rubella surveillance network (MoRoNet) in Milan and surrounding areas (Northern Italy). Between 2017 and 2021, we confirmed measles virus (genotypes B3 or D8) infections in 653 patients and 51 of these (7.8%) were vaccinees. Among vaccinated individuals whose serum was available, a secondary failure was evidenced in 69.4% (25/36) of cases while 11 patients (30.6%) were non-responders. Non-responders were more frequently hospitalized and had significantly lower Ct values in both respiratory and urine samples. Median age and time since the last immunization were similar in the two groups. Importantly, we identified onward transmissions from vaccine failure cases. Vaccinees were involved in 20 outbreaks, in 10 of them they were able to transmit the virus, and in 8 of them, they were the index case. Comparing viral hemagglutinin sequences from vaccinated and non-vaccinated subjects did not show a specific mutation pattern. These results suggest that vaccination failure was likely due to the poor immune response of single individuals and highlights the importance of identifying breakthrough cases and characterizing their clinical and virologic profiles.

Confirmed reinfection with SARS‐CoV‐2 during a pregnancy: A case report

Pregnancy might impact immunity after SARS‐CoV‐2 infection and/or vaccination. We describe the first case of reinfection with SARS‐CoV‐2 during a pregnancy. While the mother lacked detectable antibodies 2 months after the first infection, both mother and baby had IgG antibodies at delivery. Infection did not cause any adverse pregnancy outcome.

Measles seroprevalence among Dutch travelling families

BACKGROUND

While measles vaccination is widely implemented in national immunisation programmes, measles incidence rates are increasing worldwide. Dutch inhabitants who were born between 1965-1975 may have fallen between two stools, lacking protection from a natural infection, and having missed the introduction of the measles vaccination schedule. With this study we aim to find the measles seroprevalence in travellers born between 1965 and 1975, compared to those born before 1965 and after 1975.

METHODS

Families travelling to Eastern Europe or outside Europe during the preceding year were recruited via Dutch secondary schools between 2016 and 2018. Their vaccination status was assessed using questionnaires, vaccination records and measles serology in dried blood spot (DBS) eluates. Measles virus antibody concentrations were determined with an ELISA (EUROIMMUNE®) and a subset was retested with a focus reduction neutralization assay (FRNT).

RESULTS

In 188 (79%) of the 239 available DBS eluates, the ELISA could detect sufficient measles virus-specific IgG antibodies. Of the negative samples that were retested with FRNT, 85% remained negative, resulting in an overall seroprevalence of 82% [95% CI 76-86]. Children had a lower seroprevalence (72%) than adults (87%). Travellers born between 1965 and 1975 were protected in 89%.

CONCLUSIONS

In this study, we report a measles seroprevalence of 82% among Dutch travelling families. Remarkably, seroprevalence rates were lowest in children (12-18 years) instead of travellers born between 1965 and 1975. Although a fraction of people without detectable antibodies may be protected by other immune mechanisms, these data suggest that measles (re)vaccination should be considered for travellers to endemic regions.

Recurrent and persistent infection with SARS-CoV-2 - epidemiological data and case reports from Western Sweden, 2020

BACKGROUND

Reinfections with SARS-CoV-2 have been reported and most cases were classified as mild. Reports of persistent infection with SARS-CoV-2 are rare.

AIM

To investigate the frequency of recurrent and persistent infection with SARS-CoV-2.

METHODS

Possible cases of reinfection and persistent infection were retrospectively identified in a database of 59,998 patients. Deep sequencing of SARS-CoV-2 genomes was performed.

RESULTS

We report the first case of COVID-19 reinfection in Sweden and three cases of infection with persistence over several months. The rate of sequencing-verified reinfection was 0.02% (one patient out of 6014 patients testing positive during the period).

CONCLUSIONS

The reinfected patient had mild symptoms during the second episode, which might reflect partial immunity. The frequency of reinfection during the first wave of the pandemic in western Sweden was very low. Our results indicate that elderly with a putative reinfection more likely have persistent COVID-19.

Relationship between biochemical markers and measles viral load in patients with immunologically naive cases and secondary vaccine failure: LDH is one of the potential auxiliary indicators for secondary vaccine failure

This study investigated the correlation between biochemical markers and viral load among 38 measles cases, including 15 immunologically naive patients and 23 patients with secondary vaccine failure (SVF). We examined four biochemical markers, namely, aspartate aminotransferase, alanine aminotransferase, C-reactive protein, and lactate dehydrogenase (LDH) and their relationship between virus genome copy numbers in peripheral blood mononuclear cells (PBMCs) and throat swabs as well as the concentration of measles-specific IgG. Although viral genome copies in both clinical specimens showed a significant correlation with specific IgG concentration, they had a higher correlation in PBMCs (Pearson's product-moment correlation coefficient, -0.662; p < .0001) than in throat swabs (Spearman's rank correlation coefficient, -0.443; p = .0078). The viral load in PBMCs also significantly correlated with LDH values (correlation coefficient, 0.360; p = .036). Thus, the serum LDH level might be a potential auxiliary indicator to distinguish immunologically naive patients with measles from those with SVF.

Diagnostic challenges and pockets of susceptibility identified during a measles outbreak, Luxembourg, 2019

Luxembourg was among the first countries in the World Health Organization (WHO) European Region documenting interruption of endemic measles transmission, but an increased incidence was registered in spring 2019. The outbreak started with an unvaccinated student who had been to a winter sports resort in a neighbouring country, where a measles outbreak was ongoing. Subsequently, 12 secondary and two tertiary cases were confirmed among students from the same school, relatives and healthcare workers, as well as six probably unrelated cases. Only 11 cases initially fulfilled the WHO definition for suspected measles cases. Fourteen of 20 cases with information on country of birth and the majority of unvaccinated cases (10/12) were born outside of Luxembourg. Measles IgM antibody results were available for 16 of the confirmed cases, and five of the eight IgM negative cases had been vaccinated at least once. All 21 cases were PCR positive, but for three previously vaccinated cases with multiple specimen types, at least one of these samples was negative. The outbreak highlighted diagnostic challenges from clinical and laboratory perspectives in a measles elimination setting and showed that people born abroad and commuters may represent important pockets of susceptible people in Luxembourg.

Measles outbreak investigation in a highly vaccinated community in the Centre region of Cameroon

BACKGROUND

Measles remains a threat in many African settings due to sub-optimal routine immunisation and catchup campaigns. The Global Vaccine Action Plan goal to eliminate measles by 2020 remains unmet as several countries reported an increase in cases in 2019. In Cameroon, a measles-rubella vaccination campaign was organised in 2019 to reduce the cohort of susceptible children. However, in 2020, eleven suspected cases of measles were notified in the Sa'a Health District and five were confirmed.

OBJECTIVE

This report summarizes a measles outbreak investigation and contact tracing in a highly vaccinated community residing in the Sa'a Health District of Cameroon.

METHODS

Outbreak investigations were carried out in the Sa'a, Nlong-Onambele and Nkolmgbana health areas from 18 to 21 February 2020. A register review from December 2019 to February 2020 was carried out in all health facilities of the affected health areas. followed by contact tracing in the community.

RESULTS

Thirty households were visited in four neighbourhoods. Six missed Epidemiologically-linked cases were discovered in the community, bringing the total number of suspected and confirmed cases to 17. Thirty-five percent of the cases had not received any measles-containing vaccine; 35% of the cases were aged 5 years or older; 53% had history of travel. Community transmission only occurred in the Sa'a health area through a breakthrough case.

CONCLUSIONS

This outbreak investigation portrayed the role that adequate vaccination coverage plays in preventing widespread outbreaks. Nonetheless, community sensitisation and routine immunisation require strengthening in order to erase pockets of susceptible children.

A measles outbreak in Kansai International Airport, Japan, 2016: Analysis of the quantitative difference and infectivity of measles virus between patients who are immunologically naive versus those with secondary vaccine failure

Since the elimination of the measles virus, patients with vaccination records for the measles-containing vaccine have increased in Japan. According to several studies, the transmission risk from previously immunized patients, especially those with secondary vaccine failure (SVF), is lower than that from those with primary measles infections. Immunological features of SVF were identified per specific immunoglobulin G (IgG) induction with high avidity and high plaque reduction neutralization antibody concentration. However, the virological features of SVF have not been well investigated. To examine not only immunological but also virological differences between SVF and immunologically naive patients, throat swabs and blood and urine specimens of 25 patients with confirmed measles infection after an outbreak at the Kansai International Airport in 2016 were analyzed. Patients were categorized as naive (n = 3) or with SVF (n = 22) based on measles-specific IgG antibody concentrations and their avidity. Virus isolation and quantitative real-time polymerase chain reaction were performed to quantify the viral load in clinical specimens and estimate the infectivity in each specimen. The number of viral genome copies in the blood specimens of those with SVF was significantly different and approximately 1 out of 100 of that in immunologically naive patients. However, genome copy numbers in throat swabs and urine specimens were not significantly different between the groups. The virus was isolated only from those in the naive group. Our study indicated low transmission risk of the virus in patients with SVF.

Immunity to vaccine-preventable diseases among paediatric healthcare workers in Denmark, 2019

Background

Healthcare workers (HCW) have been identified as index cases in disease outbreaks of vaccine-preventable diseases (VPD) in hospitals.

Aim

We investigated whether Danish paediatric HCW were protected against selected serious VPD.

Methods

We included 90% of staff members from two paediatric departments. All 555 HCW (496 women) supplied a blood sample for serology and filled in a questionnaire. Antibodies were measured with enzyme immunoassay against measles, mumps, rubella (MMR), varicella zoster, pertussis toxin and diphtheria toxin.

Results

Protective levels of IgG were found for measles (90.3%), mumps (86.5%), rubella (92.3%), varicella (98.6%) and diphtheria (80.5%). We found seropositivity for all three MMR components in 421 (75.9%) HCW, lowest in those younger than 36 years (63.3%). Only 28 (5%) HCW had measurable IgG to pertussis. HCW with self-reported immunity defined as previous infection or vaccination, had protective levels of IgG against measles, mumps, rubella and varicella in 87.4–98.8% of cases, not significantly higher than in those not reporting immunity. Previous history of disease had a high positive predictive value (PPV) of 96.8–98.8%. The PPV for previous vaccination ranged from 82.5% to 90.3%. In contrast, negative predictive values of self-reported history of disease and vaccination were remarkably low for all diseases.

Conclusion

The immunity gaps found primarily in young HCW indicate a need for a screening and vaccination strategy for this group. Considering the poor correlation between self-reported immunity and seropositivity, efforts should be made to check HCW’s immune status in order to identify those who would benefit from vaccination.

Immunisation of healthcare workers in the Nordic countries: Variation in recommendations and practices and a lack of assessment

Healthcare workers (HCWs) are at increased risk of both exposure and transmission of infectious disease. Two European Union (EU) directives state that health services are responsible for assessing their employees’ potential exposure to infectious diseases and offering immunisation free of charge. We assessed current policy for immunisation of HCWs and the availability of vaccine coverage data in the Nordic countries by surveying national vaccination experts in Denmark, Finland, Iceland, Norway and Sweden, as well as Swedish county medical officers (CMOs). All national experts and 17 of 21 Swedish CMOs responded. All EU countries had transposed the European directives into national law, while Norway and Iceland had similar national legislation. Recommendations or guidelines were issued in Denmark, Finland, Iceland, Norway and 15 of 17 responding Swedish counties. The range of diseases covered differed by countries and Swedish counties. HCW vaccine coverage data were not systematically collected; incomplete estimates were only available for Finland and two Swedish counties. In conclusion, recommendations or guidelines exist in the Nordic countries, but their impact cannot be assessed, as vaccine uptake among HCWs is not currently measured. Systematic collection of data is a necessary step towards improving HCW immunisation policy and practice in the Nordic countries.

An efficient molecular approach to distinguish chains of measles virus transmission in the elimination phase

Measles viruses continue to spread globally, despite the availability of a safe and effective vaccine. Molecular surveillance of measles virus has become an essential tool to demonstrate whether cascades of infections in a certain region or country are the result of endemic spread or the repeatedly introduction of the virus in contained outbreaks. Currently, molecular surveillance of measles viruses worldwide is mainly based on 450 nucleotides of the C-terminal region of the nucleoprotein (N450). However, as a result of the disappearance of particular measles virus clades over the past decades, this gene segment does not provide sufficient resolution anymore to answer these questions. To increase the molecular resolution, sequence data were collected from three regions of the measles virus genome, the partial non-coding region between the M and F gene (M-F NCR_4465-4754), partial H gene (H_8022-8621) and the partial L gene (L_10724-11438) for measles viruses detected in 2018 and 2019 in the Netherlands. Analysis of obtained sequence data indicated that sequencing of these three regions resulted in an increase in molecular resolution for measles virus genotype B3 and D8 viruses, two of the four global genotypes currently predominant in the European region. Furthermore, this improved resolution was sufficient to support an epidemiology characterized by repeat introduction of measles virus rather than endemic virus spread. In conclusion, sequencing of the M-F NCR_4465-4754, H_8022-8621 and L_10724-11438 regions of the measles virus is an efficient and useful approach for molecular surveillance of measles viruses.

Lower Rate of Seropositivity to Measles Among Young Healthcare Personnel in New York City

We examined the prevalence of measles antibody among 12 349 newly hired HCP between 2009 and 2019. Younger HCP were significantly more likely to have no immunity. Compared with a 92.2% seropositive rate among 1057 persons hired at age >50 years, only 84.4% of approximately 10 000 HCP aged <40 years had protective antibody.

The digital immunization system of the future: imagining a patient-centric, interoperable immunization information system

To ensure the effectiveness of increasingly complex immunization programs in upper-middle and high-income settings, comprehensive information systems are needed to track immunization uptake at individual and population levels. The maturity of cloud systems and mobile technologies has created new possibilities for immunization information systems. In this paper, we describe a vision for the next generation of digital immunization information systems for upper-middle and high-income settings based on our experience in Canada. These systems center on the premise that the public is engaged and informed about the immunization process beyond their interaction with primary care, and that they will be a contributor and auditor of immunization data. The digital immunization system of the future will facilitate reporting of adverse events following immunization, issue digital immunization receipts, permit identification of areas of need and allow for delivery of interventions targeting these areas. Through features like immunization reminders and targeted immunization promotion campaigns, the system will reduce many of the known barriers that influence immunization rates. In light of the global COVID-19 pandemic, adaptive digital public health information systems will be required to guide the rollout and post-market surveillance of the SARS-CoV-2 vaccine.

Elevated expansion of follicular helper T cells in peripheral blood from children with acute measles infection

BACKGROUND

Measles outbreaks have threatened the global elimination and eradication of measles in recent years. Measles virus (MeV)-specific antibodies are successful in clearing MeV infection. Follicular helper T (Tfh) cells play a crucial role in promoting antibody production. This study investigated the potential role of Tfh cells in peripheral blood mononuclear cells (PBMCs) from children with acute MeV infection.

RESULTS

The frequencies of CXCR5⁺CD4⁺ Tfh, ICOS^high Tfh, and PD-1^high Tfh cells in PBMCs and levels of IL-6 and IL-21 in plasma were significantly elevated in patients with acute MeV infection. Moreover, a positive correlation was discovered among the frequency of ICOS^high Tfh cells, plasma levels of IL-21 and optical density (OD) values of MeV-specific IgM antibodies in the patients with acute MeV infection. However, elevated plasma MeV-specific NAb titres were not associated with the frequency of Tfh, ICOS^high Tfh, or PD-1^high Tfh cells in the patients with acute MeV infection.

CONCLUSION

These results suggest that an elevated Tfh cell frequency and associated molecules possibly play a key role in children with acute MeV infection, which contributes to the prevention and treatment of MeV infection in children.