Avidity maturation of humoral response following primary and booster doses of BNT162b2 mRNA vaccine among nursing home residents and healthcare workers

Infections, despite vaccination, can be clinically consequential for frail nursing home residents (NHR). Poor vaccine-induced antibody quality may add risk for such subsequent infections and more severe disease. We assessed antibody binding avidity, as a surrogate for antibody quality, among NHR and healthcare workers (HCW). We longitudinally sampled 112 NHR and 52 HCWs who received the BNT162b2 mRNA vaccine after each dose up to the Wuhan-BA.4/5-based Omicron bivalent boosters. We quantified anti-spike, anti-receptor binding domain (RBD), and avidity levels to the ancestral Wuhan, Delta, and Omicron BA.1 & 4/5 strains. The primary vaccination series produced substantial anti-spike and RBD levels which were low in avidity against all strains tested. Antibody avidity progressively increased in the 6-8 months that followed. Avidity significantly increased after the 1st booster but not for subsequent boosters. This study underscores the importance of booster vaccination among NHR and HCWs. The 1st booster dose increases avidity, increasing vaccine-induced functional antibody. The higher cross-reactivity of higher avidity antibodies to other SARS-CoV-2 strains should translate to better protection from ever-evolving strains. Higher avidities may help explain how the vaccine's protective effects persist despite waning antibody titers after each vaccine dose.

Questionable Immunity to Mumps among Healthcare Workers in Italy-A Cross-Sectional Serological Study

Highly contagious diseases, such as mumps, are a global concern as new epidemics continue to emerge, even in highly vaccinated populations. The risk of transmission and spread of these viruses is even higher for individuals who are more likely to be exposed, including healthcare workers (HCWs). In healthcare settings, both HCWs and patients are at risk of infection during the care process, potentially leading to nosocomial epidemic outbreaks. Mumps is often underestimated compared with measles and rubella, despite being milder and less likely to spread. In fact, the risk of complications following mumps infection is extremely high, especially if the disease occurs in adulthood. The measles-mumps-rubella (MMR) vaccine has been shown to be an excellent preventive measure. Unfortunately, the mumps component appears to be less effective in inducing immunity than those for measles and rubella (two-dose effectiveness of 85%, 95% and 97%, respectively). The main aim of our study was to investigate the prevalence of detectable mumps antibodies (serum IgG antibodies) in a cohort of Italian and foreign HCWs in relation to personal and occupational factors. We included in the study 468 subjects who underwent health surveillance at the Occupational Medicine Unit of the Tor Vergata Polyclinic in Rome during the period from January 2021 to March 2023. In our study, the proportion of HCWs found to be unprotected against mumps was very high (8.3%), and those found to be immune are below the WHO threshold for herd immunity (95%). From our data, it seems essential that all occupational health services carry out an accurate screening with a dose of anti-mumps antibodies to assess serological protection before starting a job, regardless of an individual's vaccination history. This approach is proving to be beneficial, accurate, as it allows all serologically non-immune individuals to be vaccinated in the workplace, including those who would be protected by their vaccination history but have lost the antibody response.

Probability of exposure to the wild measles virus in adult population - Estimation from seroepidemiology and historical data

Vaccination against measles is one of the most effective public health interventions which has saved millions of lives and interrupted circulation of the natural virus in the population. However, it is widely accepted that the immunity after vaccination can wane, especially in those who have had no contact with the virus. This study aimed to classify the particular birth cohorts of adults with regard to their exposure to the wild measles virus in the population with a long history of mandatory vaccination. We introduced two methods. In the first, we estimated the probability of exposure to the wild virus through an analysis of antibody levels from the Immunologic Survey performed in the Slovak Republic in 2018, while the second was based on historical epidemiological data. Both methods resulted in similar estimations. Cohorts born in Slovakia before 1964 can be considered to be cohorts in which most people were exposed to the wild measles virus. Cohorts born after 1977 can be designated as cohorts that most likely did not come into the contact with the wild virus. Cohorts born between 1965 and 1976 are composed of a mixture, with a decreasing proportion of people exposed to the wild virus with increasing year of birth. The proposed methods can help identify potential immunity gaps in the adult population. They can be applied in other countries with high measles vaccination coverage to estimate the probability of exposure to the wild measles virus in particular birth cohorts.

Estimation of the infection attack rate of mumps in an outbreak among college students using paired serology

Mumps virus is a highly transmissible pathogen that is effectively controlled in countries with high vaccination coverage. Nevertheless, outbreaks have occurred worldwide over the past decades in vaccinated populations. Here we analyse an outbreak of mumps virus genotype G among college students in the Netherlands over the period 2009-2012 using paired serological data. To identify infections in the presence of preexisting antibodies we compared mumps specific serum IgG concentrations in two consecutive samples (n=746), whereby the first sample was taken when students started their study prior to the outbreaks, and the second sample was taken 2-5 years later. We fit a binary mixture model to the data. The two mixing distributions represent uninfected and infected classes. Throughout we assume that the infection probability increases with the ratio of antibody concentrations of the second to first sample. The estimated infection attack rate in this study is higher than reported earlier (0.095 versus 0.042). The analyses yield probabilistic classifications of participants, which are mostly quite precise owing to the high intraclass correlation of samples in uninfected participants (0.85, 95%CrI: 0.82-0.87). The estimated probability of infection increases with decreasing antibody concentration in the pre-outbreak sample, such that the probability of infection is 0.12 (95%CrI: 0.10-0.13) for the lowest quartile of the pre-outbreak samples and 0.056 (95%CrI: 0.044-0.068) for the highest quartile. We discuss the implications of these insights for the design of booster vaccination strategies.

Immunogenicity, safety and duration of protection afforded by chikungunya virus vaccines undergoing human clinical trials

Background. Chikungunya virus (CHIKV) causes chikungunya fever and has been responsible for major global epidemics of arthritic disease over the past two decades. Multiple CHIKV vaccine candidates are currently undergoing or have undergone human clinical trials, with one vaccine candidate receiving FDA approval. This scoping review was performed to evaluate the 'efficacy', 'safety' and 'duration of protection' provided by CHIKV vaccine candidates in human clinical trials.Methods. This scoping literature review addresses studies involving CHIKV vaccine clinical trials using available literature on the PubMed, Medline Embase, Cochrane Library and Clinicaltrial.gov databases published up to 25 August 2023. Covidence software was used to structure information and review the studies included in this article.Results. A total of 1138 studies were screened and, after removal of duplicate studies, 12 relevant studies were thoroughly reviewed to gather information. This review summarizs that all seven CHIKV vaccine candidates achieved over 90 % seroprotection against CHIKV after one or two doses. All vaccines were able to provide neutralizing antibody protection for at least 28 days.Conclusions. A variety of vaccine technologies have been used to develop CHIKV vaccine candidates. With one vaccine candidate having recently received FDA approval, it is likely that further CHIKV vaccines will be available commercially in the near future.

Long-term Neutralizing Antibody Levels Against Measles and Rubella Viruses Among Adults With 3 Doses of Measles-Mumps-Rubella Vaccine

Background

A third dose of measles-mumps-rubella vaccine (MMR) may be administered for various reasons, but data on long-term immunity are limited. We assessed neutralizing antibody levels against measles and rubella among adults up to 11 years after receipt of a third MMR dose.

Methods

In this longitudinal study, healthy adults who received a third MMR dose as young adults (ages 18-28 years) were recalled around 5 years and 9-11 years after the third dose. Measles and rubella antibody levels were assessed by plaque-reduction and immunocolorimetric neutralization assays, respectively. Antibody concentrations <120 mIU/mL and <10 U/mL were considered potentially susceptible to measles and rubella, respectively. Geometric mean concentrations (GMCs) and 95% confidence intervals (CIs) over time were estimated from generalized estimating equation models.

Results

Approximately 5 and 9-11 years after receipt of the third dose, 405 and 304 adults were assessed, respectively. Measles GMC was 428 mIU/mL (95% CI, 392-468 mIU/mL) 5 years postvaccination, declining to 381 mIU/mL (95% CI, 339-428 mIU/mL) 11 years postvaccination. At the last follow-up visit (9-11 years postvaccination), 10% of participants were potentially susceptible to measles infection. Rubella GMCs were stable throughout the follow-up period (63 U/mL to 65 U/mL); none of the participants was susceptible to rubella at the last follow-up visit.

Conclusions

Eleven years after receiving a third MMR dose, measles and rubella neutralizing antibody levels remained high in adults. However, on the basis of waning antibody levels, some adults may become susceptible to measles infection over time despite receipt of 3 vaccine doses.

Prenatal Exposure to Poly- and Perfluoroalkyl Substances (2009-2014) and Vaccine Antibody Titers of Measles, Mumps, Rubella, and Varicella in Children Four to Eight Years Old from the Healthy Start Cohort

BACKGROUND

Prenatal exposures to certain poly- and perfluoroalkyl substances (PFAS) are associated with reduced humoral responses to some childhood immunizations.

OBJECTIVE

We estimated associations between prenatal PFAS exposure and child antibody titers for measles, mumps, rubella (MMR), and varicella after immunization.

METHODS

We measured serum antibody titers of 145 children (4-8 y old) enrolled in the Healthy Start cohort in Colorado, whose mothers had PFAS quantified mid-pregnancy (2009-2014). We used linear and logistic regression models to assess the relationship between five PFAS detected in > 65 % of mothers and continuous or non-high-censored ("low") antibody titers and quantile g-computation to evaluate the overall effect of the PFAS mixture.

RESULTS

Median concentrations of individual PFAS were at or below the median reported among females in the United States. After receiving two vaccine doses, seropositive levels of antibodies were detected among most (93%-100%) children. Each log-unit increase in perfluorononanoate was associated with 2.09 [95% confidence interval (CI): 1.13, 3.87] times higher odds of a low measles titer, and each log-unit increase in perfluorooctanoate was associated with 2.46 (95% CI: 1.28, 4.75) times higher odds of a low mumps titer. Odds ratios for all other PFAS were elevated, but CIs included the null. Each quartile increase in the PFAS mixture was associated with 1.35 (95% CI: 0.80, 2.26) times higher odds of a low measles titer and 1.44 (95% CI: 0.78, 2.64) times higher odds of a low mumps titer. No significant associations were observed between PFAS and varicella or rubella antibodies. In stratified analyses, associations were negative among female children, except for perfluorohexane sulfonate and varicella, whereas they were positive among males.

DISCUSSION

Some prenatal PFAS were associated with lower antibody titers among fully immunized children. The potential for immunotoxic effects of PFAS requires further investigation in a larger study, because exposure is ubiquitous globally. https://doi.org/10.1289/EHP12863.

Seroprevalence of Measles, Mumps, Rubella, and Varicella-Zoster Virus and Seroresponse to the Vaccinations in Adult Solid Organ Transplant Candidates

BACKGROUND

Updating live vaccines such as measles, mumps, rubella, and varicella (MMRV) is an important step in preparing patients for solid organ transplant (SOT) to prevent morbidity from these preventable diseases. However, data for this approach are scarce. Thus, we aimed to describe the seroprevalence of MMRV and the efficacy of the vaccines in our transplant center.

METHODS

Pre-SOT candidates >18 y of age were retrospectively retrieved from SOT database in Memorial Hermann Hospital Texas Medical Center. MMRV serologies are routinely screened at the time of pretransplant evaluation. We divided patients into 2 groups: MMRV-positive group versus MMRV-negative group, patients with positive all MMRV serologies and with negative immunity to at least 1 dose of MMRV, respectively.

RESULTS

A total of 1213 patients were identified. Three hundred ninety-four patients (32.4%) did not have immunity to at least 1 dose of MMRV. Multivariate analysis was conducted. Older age (odds ratio [OR]: 1.04) and liver transplant candidates (OR: 1.71) were associated with seropositivity. Previous history of SOT (OR: 0.54) and pancreas/kidney transplant candidates (OR: 0.24) were associated with seronegativity. Among 394 MMRV seronegative patients, 60 patients received 1 dose of MMR vaccine and 14 patients received 1 dose of varicella-zoster virus vaccine without severe adverse events. A total of 35% (13/37) of patients who had follow-up serologies did not have a serological response.

CONCLUSIONS

A significant number of pre-SOT candidates were not immune to at least 1 dose of MMRV. This highlights the importance of MMRV screening and vaccinations pre-SOT. Postvaccination serological confirmation should be performed to evaluate the necessity for a second dose.

The third dose of measles-containing vaccine induces robust immune responses against measles in young seronegative healthcare workers who had previous two-dose measles vaccination

BACKGROUND

Despite the low measles antibody positivity rate among young healthcare workers (HCWs) who have previously received two doses of a measles-containing vaccine (MCV), whether an additional dose of MCV acts as a booster remains unknown. Thus, we aimed to evaluate the immune responses to a third dose of MCV in young HCWs.

METHODS

Hospital-wide measles seroprevalence was assessed using enzyme-linked immunosorbent assay (ELISA). The immunogenicity of a third dose of MCV was determined in young seronegative HCWs (born between 1986 and 1997) who had previously received a two-dose measles vaccination.

RESULTS

A total of 3033 (92.6%) HCWs had anti-measles immunoglobulin G. The lowest seropositivity rate was observed in HCWs aged 20-24 years (87.7%). In this group, HCWs who received a third dose of MCV had higher seropositivity than those who received a second dose (89.5% vs. 75.4%). A third dose of MCV was administered to 18 HCWs who did not have anti-measles IgG despite two doses. Neutralizing antibody titers increased significantly 4 weeks after the third vaccination. Although neutralizing antibody titers decreased 1 year post vaccination, 17 (94.4%) HCWs had medium (121-900 mIU/mL) or high (>900 mIU/mL) levels. Furthermore, the third dose of MCV increased the measles virus-specific T-cell effector function.

CONCLUSIONS

The third dose of MCV induced a strong immune response against measles in young seronegative HCWs who had previously received a two-dose measles vaccination.

A perturbative approach to the analysis of many-compartment models characterized by the presence of waning immunity

The waning of immunity after recovery or vaccination is a major factor accounting for the severity and prolonged duration of an array of epidemics, ranging from COVID-19 to diphtheria and pertussis. To study the effectiveness of different immunity level-based vaccination schemes in mitigating the impact of waning immunity, we construct epidemiological models that mimic the latter's effect. The total susceptible population is divided into an arbitrarily large number of discrete compartments with varying levels of disease immunity. We then vaccinate various compartments within this framework, comparing the value of [Formula: see text] and the equilibria locations for our systems to determine an optimal immunization scheme under natural constraints. Relying on perturbative analysis, we establish a number of results concerning the location, existence, and uniqueness of the system's endemic equilibria, as well as results on disease-free equilibria. We use numerical techniques to supplement our analytical ones, applying our model to waning immunity dynamics in pertussis, among other diseases. Our analytical results are applicable to a wide range of systems composed of arbitrarily many ODEs.

Phage display sequencing reveals that genetic, environmental, and intrinsic factors influence variation of human antibody epitope repertoire

Phage-displayed immunoprecipitation sequencing (PhIP-seq) has enabled high-throughput profiling of human antibody repertoires. However, a comprehensive overview of environmental and genetic determinants shaping human adaptive immunity is lacking. In this study, we investigated the effects of genetic, environmental, and intrinsic factors on the variation in human antibody repertoires. We characterized serological antibody repertoires against 344,000 peptides using PhIP-seq libraries from a wide range of microbial and environmental antigens in 1,443 participants from a population cohort. We detected individual-specificity, temporal consistency, and co-housing similarities in antibody repertoires. Genetic analyses showed the involvement of the HLA, IGHV, and FUT2 gene regions in antibody-bound peptide reactivity. Furthermore, we uncovered associations between phenotypic factors (including age, cell counts, sex, smoking behavior, and allergies, among others) and particular antibody-bound peptides. Our results indicate that human antibody epitope repertoires are shaped by both genetics and environmental exposures and highlight specific signatures of distinct phenotypes and genotypes.

Prevention of infections including vaccination strategies in multiple myeloma

Infections are a major cause of morbidity and mortality in multiple myeloma. The increased risk for bacterial and viral infections results mainly from the disease-inherent and treatment-induced immunosuppression. Additional risk factors are older age with immune senescence, T cell depletion, polymorbidity, and male gender. Hence, every effort should be taken to reduce the risk for infections by identifying patients at higher risk for these complications and by implementing prophylactic measures, including chemoprophylaxis and immunization against various relevant pathogens. Here, we review the available evidence and provide recommendations for medical prophylaxis and vaccination in clinical practice.

Increasing seroprevalence but waning herd immunity against measles after elimination: Longitudinal seroepidemiology of measles in Osaka Prefecture, Japan, 2003-2020

Japan is one of the countries conducting longitudinal serosurveillance of vaccine-preventable diseases. We conducted surveillance of the local measles-specific antibody titer, calculated the effective reproduction number (R_e), and compared data of four terms: term 1, 2003-2006 (before the introduction of the second shot of measles-containing vaccine); term 2, 2007-2010 (early term toward measles elimination); term 3, 2011-2014 (later term toward measles elimination); and term 4, 2015-2020 (after elimination of measles in Japan). Approximately 250 sera from volunteers aged 0 to ≥ 40 years were collected and examined for measles-specific IgG using the gelatin particle agglutination (PA) method annually from 2003 to 2020. Seroprevalence and the geometric mean of the PA antibody titer were examined by term. R_e was calculated using the age-dependent proportion immune and contact matrix for each term. Of the 4,716 sera, 886 in term 1, 1,217 in term 2, 1,069 in term 3, and 1,544 in term 4 were collected. The seroprevalence gradually increased from term 1 (88.3% CI 86.0-90.3) to term 4 (95.7% CI 94.6-96.7), and the seroprevalence of term 1 was significantly lower than those of other terms (Fisher's exact test, p < 0.001), with PA titer ≥ 16 as positive. By contrast, PA antibody titers significantly decreased from term 1 (median 1,024) to term 4 (median 256) (Mann-Whitney U test, p < 0.001). With the protection level (PA titer ≥ 128 and ≥ 256) as positive, R_e gradually increased from term 1 (1.8 and 2.3) to term 4 (2.5 and 4.8, respectively). Waning levels of measles antibodies potentially increase the measles susceptibility in Osaka, Japan. This trend might imply a limitation of vaccine-induced immunity in the absence of a natural booster for wild strains after measles elimination. This study provides a cue for maintaining continuous measles elimination status in the future.

Measles Virus Neutralizing Antibody Response and Durability Two Years after One or Two Doses of Measles-Mumps-Rubella Vaccine among Young Seronegative Healthcare Workers

Although there have been several studies regarding the immunogenicity of one or two booster doses of the measles−mumps−rubella (MMR) vaccine in measles-seronegative young adults, limited data are available about how long the immune response is sustained compared with natural infection. This study included seronegative healthcare workers (HCWs) (aged 21−38 years) who received one or two doses of the measles−mumps−rubella (MMR) vaccine and HCWs with laboratory-confirmed measles infection during an outbreak in 2019. We compared neutralizing antibody titers measured using the plaque reduction neutralization (PRN) test and measles-specific immunoglobulin G (IgG) using chemiluminescent immunoassays 2 years after vaccination or infection. Among 107 HCWs with seronegative measles IgGs, the overall seroconversion rate of measles IgGs remained 82.2% (88/107), and 45.8% (49/107) of the participants had a medium (121−900) or high (>900) PRN titer after 2 years from one or two booster doses. The measles-neutralizing antibody titers of both PRN titer (ND50) and geometric mean concentration 2 years after natural infection were significantly higher than those of one or two booster doses of the MMR vaccine (p < 0.001 and p < 0.001, respectively). Our results suggest that serologic screening followed by appropriate postexposure prophylaxis can be beneficial for young HCWs without a history of natural infection especially in a measles outbreak setting, because of possible susceptibility to measles despite booster MMR vaccination 2 years ago. Long-term data about sustainable humoral immunity after one or two booster vaccination are needed based on the exact vaccination history.

Daily preventive zinc supplementation increases the antibody response against pathogenic Escherichia coli in children with zinc insufficiency: a randomised controlled trial

Zinc deficiency impairs the antibody-mediated immune response and is common in children from lower-income countries. This study aimed to investigate the impact of different zinc supplementation regimens (7, 10 or 20 mg/day elemental zinc)—therapeutic dispersible zinc tablets (TZ), daily multiple micronutrient powder (MNP), daily preventive zinc tablets (PZ) and placebo powder (control)—and compare between baseline and endline antibody production against pathogenic Escherichia coli in Laotian children (aged 6–23 months). Fifty representative plasma samples of each treatment group were randomly selected from 512 children to determine anti-E. coli IgG antibody levels and avidity. Of the 200 children, 78.5% had zinc deficiency (plasma zinc concentration < 65 µg/dL) and 40% had anaemia before receiving zinc supplementation. aAfter receiving the TZ, MNP or PZ regimen, the plasma anti-E. coli IgG levels were significantly increased compared with baseline; the effect on the antibody level was more pronounced in children with zinc deficiency. Interestingly, there was increased anti-E. coli IgG avidity in the control and PZ groups. This study suggests that PZ might be the optimal zinc supplementation regimen to increase both the quantity and quality of antibody responses in children with zinc deficiency. Clinical trial registration: https://clinicaltrials.gov/ct2/show/NCT02428647 (NCT02428647, 29/04/2015).

Changing demographics and immunity to vaccine preventable diseases in people with HIV in Ireland

BACKGROUND

HIV infection is associated with an increased risk of morbidity and mortality from vaccine preventable infections. This research describes, in the context of changing patient demographics, the seroprevalence of vaccine preventable viral infections among attendees of the largest centre for HIV positive patients in Ireland.

METHODS

Baseline serum IgG results for measles, mumps, rubella, varicella zoster virus (VZV) & hepatitis A, as well as hepatitis B sAg, cAb and sAb results, were retrieved for 2534 clinic attendees attending in 2018. Results were available for between 990 and 2363 attendees (39-93%), depending on the test, and were compared with 2013 clinic data.

RESULTS

There was a 35% increase in attendees in 2018 when compared to 2013. The largest increase was in attendees of South American origin. In 2018, males accounted for 73% of the entire cohort and the HIV acquisition risk for 48% of attendees was MSM. 47% of attendees were originally from Ireland. Among those tested, 33% were susceptible to at least one component of the MMR vaccine. 5% were VZV non-immune (significantly associated with younger age and the acquisition risk status of injection drug use). 21% were hepatitis A non-immune (significantly associated with younger age and being of European or South American origin). 32% were hepatitis B cAb seropositive (significantly associated with older age, injection drug use status and being originally from Africa). 3% demonstrated hepatitis B sAg positivity. 64% had hepatitis B sAb ≥ 10mIU.

CONCLUSION

In a cohort of attendees to an HIV clinic in a large urban setting, the susceptibility to several common vaccine preventable viral infections, in particular MMR and hepatitis A and B, was high. These results highlight the importance of proactive screening and immunisation to help protect this high risk patient group against vaccine preventable diseases.

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.

Population immunity to measles in Canada using Canadian Health Measures survey data - A Canadian Immunization Research Network (CIRN) study

We aimed to determine population immunity to measles in Canada, and to assess the risk of future outbreaks. We tested 11,176 sera from Cycles 2 (2009-2011) and 3 (2011-2013) cohorts from the biobank of Statistics Canada's Canadian Health Measures Survey (CHMS) using the BioPlex 2220 MMRV IgG assay. We then tested all BioPlex negative and equivocal samples using a more sensitive Plaque Reduction Neutralization Test (PRNT). We determined the weighted proportion of positive, equivocal, and negative samples by age, sex, region and whether individuals were born in Canada. We found that 90.0% (95% confidence interval (CI): 88.2, 91.9) of samples were positive, 4.5% (95% CI: 3.4, 5.5) were equivocal and 5.5% (95% CI: 4.3, 6.7) were negative. Individuals in the 12-19 year age band had the lowest proportion positive at 78.7% (95% CI: 74.2, 83.2) and the highest proportion of positive samples was found in those 60-79 years (99.6%, 95% CI: 99.3, 99.9). Seropositivity was consistently <90% across a broad range of pediatric and adult age bands (6-39 years). We found that a slightly higher proportion of females were positive (91.9%, 95% CI: 90.1, 93.6) compared to males (88.3%, 95% CI: 85.8, 90.7). When taking into account interaction between age and born in Canada status, we found individuals born in Canada aged 19 and under were less susceptible (OR = 0.6 (95% CI: 0.4, 0.95)) compared to those born outside Canada whereas, those aged 20 and over were more susceptible (OR = 1.7 (95% CI: 1.1, 2.8)). Our findings indicate that measles immunity in Canada is below the 95% immunity threshold required to sustain measles elimination, underscoring the importance of maintaining high vaccine coverage to prevent future measles outbreaks and sustain Canada's elimination status.

Humoral Response to BNT162b2 Vaccine Against SARS-CoV-2 Variants Decays After Six Months

SARS-CoV-2 vaccines have shown very high effectiveness in real-world scenarios. However, there is compelling evidence for a fast-paced waning of immunity. The increasing number of new variants that could alter the severity, transmissibility, and potential to evade the immune response raised significant concern. Therefore, elucidating changes in the humoral immune response against viral variants induced by vaccines over time is crucial for improving immunization protocols. We carried out a 6-month longitudinal prospective study in which 60 individuals between 21 and 71 years of age who have received the complete scheme of the BNT162b2 vaccine were followed to determine titers of serum neutralizing activity. The neutralizing capacity was measured at one, three, and six-months post-vaccination by plaque reduction neutralization assay using SARS-CoV-2 B.1 (D614G) and the Gamma, Alpha, Delta, and Mu variants. Data were analyzed using GraphPad 5.0. Neutralizing activity against five different SARS-CoV-2 variants was detected in the serum samples of all vaccinated participants to a different extent after one month, with a progressive decrease according to age and gender. Overall, after one month of vaccination, the neutralizing titer was lower for all evaluated variants when compared to B.1, most remarkable against Delta and Mu, with a reduction of 83.1% and 92.3%, respectively. In addition, the Titer at 3- or 6-months follow-up decreased dramatically for all variants. Our results support the decaying of serum neutralizing activity, both over time and across SARS-CoV-2 variants, being more significant in older men. Since Delta and Mu appear to evade the neutralizing activity, these and further new variants of immune escape mutations should be considered for novel vaccine formulations.

Antibody Levels at 3-Years Follow-Up of a Third Dose of Measles-Mumps-Rubella Vaccine in Young Adults

Mumps outbreaks and breakthrough infections of measles and rubella have raised concerns about waning of vaccine-induced immunity after two doses of measles-mumps-rubella (MMR) vaccination. In the present follow-up study, serum IgG antibodies against mumps, measles and rubella, as well as the functional neutralizing antibodies against both the mumps vaccine strain and mumps outbreak strains were measured longitudinally in young adults that received a third MMR (MMR3) dose. The mumps-specific IgG and virus neutralizing antibody levels at 3 years after vaccination were still elevated compared to pre-vaccination antibody levels, although the differences were smaller than at earlier timepoints. Interestingly, subjects with low antibody levels to mumps before vaccination benefited the most as they showed the strongest antibody increase after an MMR3 dose. Three years after an MMR3 dose, all subjects had antibody levels to measles and rubella above the internationally agreed antibody cutoff levels for clinical protection. Our data support the recommendation that an MMR3 dose may provide additional protection for those that have become susceptible to mumps virus infection during outbreaks. MMR3 also resulted in an increase in anti-measles and rubella antibody levels that lasted longer than might have been expected.

Seroconversion rates following 2 doses of measles- mumps- rubella vaccination given at the ages 12 and 18 months: data for possible additional dose at older age

Background

Despite high rate of vaccination coverage with 2-doses of measles containing vaccine among Iranian children, outbreaks of measles occurred among different age groups and fully vaccinated subjects. Although the main reason for these outbreaks is unknown, however, vaccine failure was supposed to be an important cause. This study was designed to determine the seroconversion rates to measles- mumps- rubella (MMR) vaccine currently in use among Iranian children.

Methods

This prospective study was conducted among healthy children older than 12 months who were candidates of scheduled MMR vaccination. Blood samples were obtained from each mother- infant pair just before vaccination, and from infants 4–6 weeks after MMR₁ and MMR₂ immunization. Collected sera were tested for specific lgG antibodies against MMR agents using ELISA method. The proportion of seroprotected subjects among mother- infant pairs before vaccination as well as the prevalence rates of seroconversion after MMR₁ and MMR₂ vaccination were calculated. Collected data were analyzed using descriptive statistical methods.

Results

During 22-months study period, 92 mother- infant pairs were participated. Seroimmunity rates against MMR viruses were 85.8%, 84.7% and 86.9% for mothers, and 3.2%, 2.1% and 1.0% for children, respectively. After MMR₁ vaccination from 52 seronegative children, 80.7%, 78.8% and 75% were seroconverted. These rates increased to 94.8%, 89.7% and 94.8% after the MMR₂ vaccination. Also, the specific immunity was enhanced among seropositive children.

Conclusion

Majority of the mothers and few infants were immune to MMR viruses prior to MMR₁ vaccination. Immune responses detected after MMR₁ injection, and overall seroconversion rates achieved after 2-doses of MMR vaccination were less than expected and inadequate to preserve long-term protection against MMR agents.

Control of a nosocomial measles outbreak among previously vaccinated adults in a population with high vaccine coverage: Korea, 2019

We describe a measles outbreak among previously vaccinated healthcare workers (HCWs) and inpatients and the control measures implemented at a tertiary care hospital in 2019. Case-patients were laboratory-confirmed measles with throat swabs tested by quantitative polymerase chain reactions (PCR), during April-May 2019. Medical histories and documented immunization records were obtained. We compared attack rates (ARs) among HCWs by occupational subgroup and age and examined the outbreak-associated costs. The index case was not ascertained. Among 26 measles case-patients (22 HCWs, four inpatients) aged 18-28 years, 25 had previously received measles-mumps-rubella (MMR) vaccine (12/26, 46% (two doses); 13/26, 50% (one dose)), and 16 (62%) had positive results of measles IgG prior to measles diagnosis. ARs were higher among HCWs aged < 30 years (1.88%), especially in the subgroup under 25 years of age (2.22%). Control measures included work restrictions for seronegative HCWs (218/2320, 9.4%) in immunity verification, administration of the MMR vaccine (207 HCWs) or intravenous immunoglobulin (2 HCWs and 11 inpatients), enhanced health surveillance of HCWs, and mandatory assessment of patients with measles-like symptoms at the infectious diseases screening units. The hospital spent 90,417,132 Korean won (US $79,733) in response to the outbreak. Measles outbreaks can occur in healthcare settings despite high population immunity, highlighting the importance of stronger vaccination policies, particularly among young HCWs. Moreover, an effective outbreak response comprising immunization activities and enhanced surveillance of HCWs and patients to rapidly detect measles-like symptoms at a prodromal phase is essential to control nosocomial measles outbreaks.

A Polylactide-Based Micellar Adjuvant Improves the Intensity and Quality of Immune Response

Micelles from amphiphilic polylactide-block-poly(N-acryloxysuccinimide-co-N-vinylpyrrolidone) (PLA-b-P(NAS-co-NVP)) block copolymers of 105 nm in size were characterized and evaluated in a vaccine context. The micelles were non-toxic in vitro (both in dendritic cells and HeLa cells). In vitro fluorescence experiments combined with in vivo fluorescence tomography imaging, through micelle loading with the DiR near infrared probe, suggested an efficient uptake of the micelles by the immune cells. The antigenic protein p24 of the HIV-1 was successfully coupled on the micelles using the reactive N-succinimidyl ester groups on the micelle corona, as shown by SDS-PAGE analyses. The antigenicity of the coupled antigen was preserved and even improved, as assessed by the immuno-enzymatic (ELISA) test. Then, the performances of the micelles in immunization were investigated and compared to different p24-coated PLA nanoparticles, as well as Alum and MF59 gold standards, following a standardized HIV-1 immunization protocol in mice. The humoral response intensity (IgG titers) was substantially similar between the PLA micelles and all other adjuvants over an extended time range (one year). More interestingly, this immune response induced by PLA micelles was qualitatively higher than the gold standards and PLA nanoparticles analogs, expressed through an increasing avidity index over time (>60% at day 365). Taken together, these results demonstrate the potential of such small-sized micellar systems for vaccine delivery.

Streamlined Whole Genome Sequencing of Mumps for High Resolution Outbreak Analysis

Since 2015, the United States has experienced a resurgence in the number of mumps cases and outbreaks in fully vaccinated populations. These outbreaks have occurred predominantly in close quarter settings such as camps, colleges and detention centers. Phylogenetic analysis of 758 mumps positive samples from outbreaks across the United States, identified 743 (98%) as genotype G based on sequence analysis of the mumps small hydrophobic (SH) gene. Additionally, SH sequences in the genotype G samples showed almost no sequence diversity, with 675 (91%) of them having identical sequences or only one nucleotide difference. This uniformity of circulating genotype and strain created complications for epidemiologic investigations and necessitated the development of a system for rapidly generating mumps whole genome sequences for more detailed analysis. In this study, we report a novel and streamlined assay for whole genome sequencing (WGS) of mumps virus genotype G. The WGS procedure successfully generated 318 high-quality WGS sequences on nucleic acid from genotype G-positive respiratory samples collected during several mumps outbreaks in the United States between 2016-2019. Sequencing was performed by a rapid and highly sensitive custom Ion AmpliSeq mumps genotype G panel, with sample preparation performed on an Ion Chef and sequencing on an Ion S5. The WGS data generated by the AmpliSeq panel provided enhanced genomic resolution for epidemiological outbreak investigations. Translation and protein sequence analysis also identified several potentially important epitope changes in the circulating mumps genotype G strains compared to the Jeryl-Lynn strain (JL5) used in vaccines in the United States which could explain the current level of vaccine escapes.

Assessment of avidity related to IgG subclasses in SARS-CoV-2 Brazilian infected patients

SARS-CoV-2 is considered a global emergency, resulting in an exacerbated crisis in the health public in the world. Although there are advances in vaccine development, it is still limited for many countries. On the other hand, an immunological response that mediates protective immunity or indicates that predict disease outcome in SARS-CoV-2 infection remains undefined. This work aimed to assess the antibody levels, avidity, and subclasses of IgG to RBD protein, in symptomatic patients with severe and mild forms of COVID-19 in Brazil using an adapted in-house RBD-IgG ELISA. The RBD IgG-ELISA showed 100% of specificity and 94.3% of sensibility on detecting antibodies in the sera of hospitalized patients. Patients who presented severe COVID-19 had higher anti-RBD IgG levels compared to patients with mild disease. Additionally, most patients analyzed displayed low antibody avidity, with 64.4% of the samples of patients who recovered from the disease and 84.6% of those who died in this avidity range. Our data also reveals an increase of IgG1 and IgG3 levels since the 8th day after symptoms onset, while IgG4 levels maintained less detectable during the study period. Surprisingly, patients who died during 8–14 and 15–21 days also showed higher anti-RBD IgG4 levels in comparison with the recovered (P < 0.05), suggesting that some life-threatening patients can elicit IgG4 to RBD antibody response in the first weeks of symptoms onset. Our findings constitute the effort to clarify IgG antibodies' kinetics, avidity, and subclasses against SARS-CoV-2 RBD in symptomatic patients with COVID-19 in Brazil, highlighting the importance of IgG antibody avidity in association with IgG4 detection as tool laboratory in the follow-up of hospitalized patients with more significant potential for life-threatening.

Incomplete IgG avidity maturation after seasonal coronavirus infections

In classical viral infections, the avidity of immunoglobulin G (IgG) is low during acute infection and high a few months later. As recently reported, SARS-CoV-2 infections are not following this scheme, but they are rather characterized by incomplete avidity maturation. This study was performed to clarify whether infection with seasonal coronaviruses also leads to incomplete avidity maturation. The avidity of IgG toward the nucleoprotein (NP) of the seasonal coronaviruses 229E, NL63, OC43, HKU1 and of SARS-CoV-2 was determined in the sera from 88 healthy, SARS-CoV-2-negative subjects and in the sera from 70 COVID-19 outpatients, using the recomLine SARS-CoV-2 assay with recombinant antigens. In the sera from SARS-CoV-2-negative subjects, incomplete avidity maturation (persistent low and intermediate avidity indices) was the lowest for infections with the alpha-coronaviruses 229E (33.3%) and NL63 (61.3%), and the highest for the beta-coronaviruses OC43 (77.5%) and HKU1 (71.4%). In the sera from COVID-19 patients, the degree of incomplete avidity maturation of IgG toward NP of 223E, OC43, and HKU1 was not significantly different from that found in SARS-CoV-2-negative subjects, but a significant increase in avidity was observed for IgG toward NP of NL63. Though there was no cross-reaction between SARS-CoV-2 and seasonal coronaviruses, higher concentrations of IgG directed toward seasonal coronaviruses seemed to indirectly increase avidity maturation of IgG directed toward SARS-CoV-2. Our data show that incomplete IgG avidity maturation represents a characteristic consequence of coronavirus infections. This raises problems for the serological differentiation between acute and past infections and may be important for the biology of coronaviruses.

Seroprevalence of Measles-, Mumps-, and Rubella-specific antibodies in the German adult population - cross-sectional analysis of the German Health Interview and Examination Survey for Adults (DEGS1)

BACKGROUND

The WHO European Region targets the elimination of measles, rubella, and the congenital rubella syndrome and welcomes mumps elimination via the joint MMR vaccine. In a push towards this elimination goal, Germany introduced a recommendation on MMR vaccination for adults in 2010 to prevent increasing numbers of measles cases among adults and to strengthen herd immunity.

METHODS

The prevalence of anti-measles, -mumps, and -rubella IgG antibodies was analysed in 7,115 participants between the ages of 18 and 79 years in the German Health Interview and Examination Survey. Risk factors of seronegativity of adults born 1970 or later were determined.

FINDINGS

The seroprevalence of anti-measles IgG antibodies was more than 97% in adults born before 1965 and less than 90% in adults born afterwards. Prevalence and GMTs declined with later years of birth. Seronegativity was associated with two-sided migration background and region of residence in East Germany. For anti-mumps IgG antibodies, the seroprevalence was less than 90% in almost all age groups. Prevalence and GMTs declined with later years of birth. Seronegativity was not associated with any socio-demographic factor. Anti-rubella IgG seropositivity was found in more than 90% of adults born before 1985. GMTs declined in younger age groups. Seronegativity was associated with birth between 1980 and 1993 and male gender. High socio-economic status lowered the odds of being seronegative.

INTERPRETATION

These data reinforce the implementation of the vaccination recommendation for adults and provide the basis for further evaluation of this measure.

FUNDING

The Federal Ministry of Health, Germany.

Optimizing virus protection in lung transplant recipients: Don't drop the ball

Meyer and Avery comment on the implications of a study by Hostetler et al. (page 2864), in which screening of a large group of lung transplant candidates revealed that some lacked humoral immunity to measles, mumps, and varicella, especially younger patients and those with cystic fibrosis.

Novel mumps virus epitopes reveal robust cytotoxic T cell responses after natural infection but not after vaccination

Mumps is nowadays re-emerging despite vaccination. The contribution of T cell immunity to protection against mumps has not been clearly defined. Previously, we described a set of 41 peptides that were eluted from human leukocyte antigen (HLA) class I molecules of mumps virus (MuV)-infected cells. Here, we confirmed immunogenicity of five novel HLA-B*07:02- and HLA-A*01:01-restricted MuV T cell epitopes from this set of peptides. High frequencies of T cells against these five MuV epitopes could be detected ex vivo in all tested mumps patients. Moreover, these epitope-specific T cells derived from mumps patients displayed strong cytotoxic activity. In contrast, only marginal T cell responses against these novel MuV epitopes could be detected in recently vaccinated persons, corroborating earlier findings. Identifying which MuV epitopes are dominantly targeted in the mumps-specific CD8⁺ T- response is an important step towards better understanding in the discrepancies between natural infection or vaccination-induced cell-mediated immune protection.

Evaluation of Immunity for Mumps among Vaccinated Medical Students

Healthcare workers are considered at higher risk for mumps infection than the general population. Since 2017, the national immunization plan recommended the administration of a dose of measles–mumps–rubella (MMR) vaccine to the healthcare operators who are unable to demonstrate a complete vaccination history or that are seronegative for at least one of the three agents. Regarding mumps infection, based on actual concerns regarding the loss of protection over the years after vaccination, the Advisory Committee on Immunization Practices (ACIP) recommended to administer a third dose of vaccine to operators previously vaccinated with two doses of MMR vaccine who belong to a group at increased risk of mumps infection in the event of an epidemic. This guideline, however, is not currently followed in Italy, resulting in a potential risk for vaccinated operators to become unprotected from mumps over the years. The aim of our study is to evaluate the persistence of a protective antibody level for mumps among medical students vaccinated during infancy or adolescence, at the start of their hospital internship. We retrospectively evaluated mumps-specific IgG levels in a group of medical students, in the period from 1 January to 31 December 2020. We evaluated the persistence of the detectable level of mumps-specific antibodies in relation to their vaccinal status, gender and time elapsed from vaccination. We found that 17.4% (65 subjects) of our sample were seronegative for mumps. The univariate analysis showed a significant difference in serological protection between male and female gender (77.0% vs. 86.2%; p < 0.05 with chi² test) and between age classes (86.5% vs. 76.4%; p < 0.05 for subjects aged 18–23 years and over 23 years, respectively). Female gender was significantly related to higher serological protection even after adjusting for age classes and number of vaccine doses administered in a multivariate analysis model. Our study shows a substantial percentage of subjects lacking a protective mumps titer among medical students who were vaccinated in childhood. Given the higher risk of infection among those subjects, routine pre-employment screening should be performed among those operators regardless of their vaccination history and a third dose of MMR should be offered to unprotected students.

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.

A durable protective immune response to wild-type measles virus infection of macaques is due to viral replication and spread in lymphoid tissues

Infection with wild-type (WT) measles virus (MeV) is an important cause of childhood mortality that leads to lifelong protective immunity in survivors. WT MeV and the live-attenuated MeV used in the measles vaccine (LAMV) are antigenically similar, but the determinants of attenuation are unknown, and protective immunity induced by LAMV is less robust than that induced by WT MeV. To identify factors that contribute to these differences, we compared virologic and immunologic responses after respiratory infection of rhesus macaques with WT MeV or LAMV. In infected macaques, WT MeV replicated efficiently in B and T lymphocytes with spreading throughout lymphoid tissues resulting in prolonged persistence of viral RNA. In contrast, LAMV replicated efficiently in the respiratory tract but displayed limited spread to lymphoid tissue or peripheral blood mononuclear cells. In vitro, WT MeV and LAMV replicated similarly in macaque primary respiratory epithelial cells and human lymphocytes, but LAMV-infected lymphocytes produced little virus. Plasma concentrations of interleukin-1β (IL-1β), IL-12, interferon-γ (IFN-γ), CCL2, CCL11, CXCL9, and CXCL11 increased in macaques after WT MeV but not LAMV infection. WT MeV infection induced more protective neutralizing, hemagglutinin-specific antibodies and bone marrow plasma cells than did LAMV infection, although numbers of MeV-specific IFN-γ- and IL-4-producing T cells were comparable. Therefore, MeV attenuation may involve altered viral replication in lymphoid tissue that limited spread and decreased the host antibody response, suggesting a link between lifelong protective immunity and the ability of WT MeV, but not LAMV, to spread in lymphocytes.

Risk of Absence of Measles Antibody in Healthcare Personnel and Efficacy of Booster Vaccination

We aimed to identify the presence of the measles IgG antibody (mIgG-Ab) in healthcare personnel and finding out who needs the measles vaccination. The history of measles vaccination was obtained from the national vaccine registry. A baseline mIgG-Ab test was performed, and the measles vaccine was administered to participants who tested negative or equivocal for mIgG-Abs. During the study, 2885 (87.3%) of the 3303 employees were tested for measles serostatus. The baseline seropositivity rate for mIgG-Abs was 91.9%. Among the 234 seronegative cases, 82.9% were born after 1985. The seroprevalence rate was lower in those who received the measles–mumps–rubella (MMR) vaccine >10 years before the testing time, especially if they were born after 1985 and if there was only one previous record of vaccination. Among the 234 seronegative cases, MMR vaccination was administered in 174 cases, of which serostatus was evaluated in 146 cases. After the first dose, positive seroconversion was achieved in 126 participants (86.3%). After a second dose, 15 achieved (75.0%) positive seroconversion. In healthcare personnel born after the period when measles incidence significantly decreased, it may be necessary to reassess their immune status for measles if more than 10 years have elapsed since the last vaccination.

Measles and rubella serosusceptibity among population vaccinated with different schedules: the potential impact on measles-rubella elimination in Iran

BACKGROUND

Iranian children were vaccinated with the scheduled two doses of monovalent measles vaccine (mMV) from 1984. In December 2003, a nationwide campaign of measles-rubella (MR) immunization was established to vaccinate 5-25 year- old individuals. In 2004, the mMV was replaced with measles- mumps- rubella (MMR) vaccine. Despite the high vaccination coverage, the outbreaks of measles still occur in the country. In this Study, the MR immunity status of various age groups, vaccinated with different schedules was investigated, and the immunologic response of seronegative subjects to revaccination was examined.

METHODS

This cross-sectional study was conducted among 7-33-year-old healthy individuals with a documented history of measles vaccination from November 2017 to June 2018. The subjects were categorized as follows: group A, including 20-33 year-old individuals; vaccinated with 1-2 doses of mMV at ages 9 and 15 months, and revaccinated with MR, group B, including 15-19-year-old individuals, vaccinated with two doses of mMV at 9 and 15 months of age, and received additional dose of MMR upon school entrance, group C, including 11-14 year-old individuals, vaccinated with two-doses of MMR at the ages of 15 months and 6 years, and group D, including 7-10 year-old individuals vaccinated with two-doses of MMR vaccine at the ages 12 and 18 months, respectively. Levels of antimeasles- antirubella IgG antibodies in the collected sera were measured. Also antimeasles- antirubella IgM and IgG of seronegative individuals were reexamined at 4-6 weeks after MMR revaccination. The collected data were analyzed using descriptive statistical methods.

RESULTS

A total of 635 individuals were investigated in this study. Group A, 98; group B, 295; group C, 139; and group D, 103 persons. Overall, 12.3 and 18.4% of the population were seronegative for measles and rubella antibodies. This rate varied greatly between the 4 groups: group A, 0/0-2%; group B,15.2-25.0%; group C,11.5-17.2%; and groupD,14.6-18.4%. After revaccination, 92 and 94.9% of seronegative individuals showed IgG response to measles and rubella vaccines, respectively.

CONCLUSION

Despite the high coverage rate of M-R containing vaccines, a significant number of vaccinated subjects were seronegative for measles and rubella, possibly because of secondary vaccine failure; this may negatively affect measles-rubella elimination targets in the country. If these findings are confirmed in similar future studies, a more robust regional/national supplementary immunization activity will be considered.

The potential significance of high avidity immunoglobulin G (IgG) for protective immunity towards SARS-CoV-2

Background

Avidity is defined as the strength of binding between immunoglobulin G (IgG) and its specific target epitope. IgG of high avidity is established during affinity maturation. Failure to achieve high avidity IgG may result in a lack of protective immunity towards infection and disease. It is known that the interaction between SARS-CoV-2 spike protein and its cellular receptor is driven by high affinity. Therefore, it is predictable that protective antibodies towards SARS-CoV-2 should show high affinity/avidity.

Avidity after SARS-CoV-2 infection

Recent findings by several groups demonstrate that the serological response towards infection with SARS-CoV-2 and seasonal coronaviruses is characterized by incomplete avidity maturation, followed by a decline of the serological response. This response might facilitate reinfection, prevent herd immunity and potentially allow repeated cycles of infection.

Consequences for vaccination towards SARS-CoV-2

Therefore, the sole focus on antibody titers reached after vaccination towards SARS-CoV-2 might not be sufficient to evaluate the degree of achieved protection. Rather, it is suggested to include avidity determination to optimize vaccination protocols and achieve high avidity IgG directed towards SARS-CoV-2 through vaccination. Avidity determination might also be useful to control for truly protective immunity towards SARS-CoV-2 in individual cases.

The challenge of avidity determination in SARS-CoV-2 serology

The serological responses towards severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) nucleoprotein, receptor‐binding domain (RBD), and spike protein S1 are characterized by incomplete avidity maturation. Analysis with varying concentrations of urea allows to determine distinct differences in avidity maturation, though the total process remains at an unusually low level. Despite incomplete avidity maturation, this approach allows to define early and late stages of infection. It therefore can compensate for the recently described irregular kinetic patterns of immunoglobulin M and immunoglobulin G (IgG) directed towards SARS‐CoV‐2 antigens. The serological responses towards seasonal coronaviruses neither have a negative nor positive impact on SARS‐CoV‐2 serology in general. Avidity determination in combination with measurement of antibody titers and complexity of the immune response allows to clearly differentiate between IgG responses towards seasonal coronaviruses and SARS‐CoV‐2. Cross‐reactions seem to occur with very low probability. They can be recognized by their pattern of response and through differential treatment with urea. As high avidity has been shown to be essential in several virus systems for the protective effect of neutralizing antibodies, it should be clarified whether high avidity of IgG directed towards RBD indicates protective immunity. If this is the case, monitoring of avidity should be part of the optimization of vaccination programs.

Avidity maturation of immunoglobulin G (IgG) towards severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) antigens is distinct, but incomplete in most cases

Nevertheless, avidity determination allows to differentiate between acute and past SARS CoV‐infection

Avidity maturation is instrumental for differentiation between IgG responses towards SARS‐CoV‐2 and seasonal coronaviruses

It is suggested to clarify whether high avidity is required for and indicative of protective immunity.

What Is the Evidence to Support a Correlate of Protection for Measles? A Systematic Review

BACKGROUND

Many studies assume that the serologic correlate of protection from measles disease is 120 mIU/mL. We systematically reviewed the literature to examine the evidence supporting this correlate of protection.

METHODS

We searched peer-reviewed and gray literature for articles reporting a measles correlate of protection. We excluded studies focusing on special populations, infants aged <9 months, and those using animal models or nonstandard vaccines or administration routes. We extracted and synthesized data from full-text articles that met inclusion criteria.

RESULTS

We screened 14 778 articles and included 5 studies in our review. The studies reported either preexposure antibody concentrations of individuals along with a description of symptoms postexposure, or the proportion of measles cases that had preexposure antibody concentrations above a threshold of immunity specified by the authors. Some studies also described secondary antibody responses upon exposure. The variation in laboratory methods between studies made comparisons difficult. Some of the studies that assumed 120 mIU/mL as a correlate of protection identified symptomatic individuals with preexposure titers exceeding this threshold.

CONCLUSIONS

Our findings underscore the scant data upon which the commonly used 120 mIU/mL measles threshold of protection is based, suggesting that further work is required to characterize the measles immunity threshold.

Immunogenicity, duration of protection, effectiveness and safety of rubella containing vaccines: A systematic literature review and meta-analysis

BACKGROUND

Rubella containing vaccines (RCV) prevent rubella virus infection and subsequent congenital rubella syndrome (CRS). To update the evidence on immunogenicity, duration of protection, effectiveness and safety of RCV, we conducted a systematic literature review.

METHODS

We searched EMBASE and SCOPUS, using keywords for rubella vaccine in combination with immunogenicity (seroconversion and seropositivity), duration of protection, efficacy/effectiveness, and safety. Original research papers involving at least one dose of RCV (at any age), published between 1-1-2010 and 17-5-2019 were included. Where appropriate, meta-analyses were performed. Quality of included studies was assessed using GRADE methodology.

RESULTS

We included 36 papers (32 randomized controlled trials (RCTs) and 4 observational studies) on immunogenicity (RA27/3 strain) in children and adolescent girls, 14 papers (5 RCTs and 9 observational studies) on duration of protection, one paper on vaccine effectiveness (VE) (BRDII strain), and 74 studies on safety, including three on safety in pregnancy. Meta-analysis of immunogenicity data showed 99% seroconversion (95% CI: 98-99%) after a single dose of RCV in children, independent of co-administration with other vaccines. Seroconversion after RCV1 below 9 months of age (BRDII strain, at 8 months) was 93% (95% CI: 92-95%). For duration of protection, the included studies showed a seropositivity of 88%-100% measured 1-20 years after one or two RCV doses. The single study on VE of BRDII strain, reported 100% VE after one and two doses. Among 34,332 individuals participating in the RCTs, 140 severe adverse events (SAEs) were reported as possibly related to RCV. Among the case reports on SAEs, the association with RCV was confirmed in one report (on fulminant encephalitis). Among 3,000 pregnant women who were inadvertently vaccinated, no SAEs were reported.

CONCLUSIONS

One and two doses of RCV are highly immunogenic for a long period of time, effective in preventing rubella and CRS, and safe.

A Third Dose of Measles-Mumps-Rubella Vaccine to Improve Immunity Against Mumps in Young Adults

BACKGROUND

Waning of vaccine-induced immunity is considered to play a central role in the reemergence of mumps among vaccinated young adults. The aim of the present study was to investigate antibody responses and safety of a third dose of measles-mumps-rubella vaccine (MMR-3) in 150 young adults. Antibody levels were related to a surrogate of protection based on preoutbreak serum antibody levels in 31 persons with and 715 without serological evidence of mumps.

METHODS

Mumps virus-specific immunoglobulin G (IgG) antibody responses and mumps virus-neutralizing antibody responses (based on the focus-reduction neutralizing test) against both the Jeryl Lynn mumps virus vaccine strain (hereafter, the "vaccine strain") and the MuVi/Utrecht.NLD/40.10 outbreak strain (hereafter, the "outbreak strain") were determined, and vaccine safety was evaluated.

RESULTS

Four weeks following MMR-3 receipt, levels of IgG, anti-vaccine strain, and anti-outbreak strain antibodies increased by a factor of 1.65, 1.34, and 1.35, respectively. Although antibody levels decreased 1 year later, they were still above the baseline level by a factor of 1.37, 1.15, and 1.27, respectively. Based on the surrogate protective antibody cutoff, significantly more participants were protected against mumps virus infection up to 1 year after vaccination (ie, they had antibody levels above the presumed threshold for herd immunity).

CONCLUSIONS

MMR-3 receipt increased antibody levels that may protect against mumps virus infection for longer than previously assumed and is expected to be a good and safe intervention for controlling a mumps outbreak.

CLINICAL TRIALS REGISTRATION

2016-001104-36; NTR5911.

Dynamics of the Antibody Response After a Third Dose of Measles-Mumps-Rubella Vaccine Indicate a Slower Decline Compared With a Second Dose

Background

Breakthrough infections of measles and mumps have raised concerns about the duration of vaccine-induced immunity, which might be improved by a third dose of measles-mumps-rubella vaccine (MMR3).

Methods

Here we compared (IgG) antibody levels against measles, mumps, and rubella in blood samples of 9-year-old children and young adults (18–25 years) following MMR2 and MMR3, respectively.

Results

We found that, in addition to antibody boosting for all 3 vaccine components, MMR3 resulted in lower antibody decay rates than MMR2; the declines were most prominent for mumps and rubella.

Conclusions

This study suggests that MMR3 provides long-lasting seroprotection against measles, mumps, and rubella.

Seroprevalence for vaccine-preventable diseases among Italian healthcare workers

Healthcare workers (HCWs) have an increased risk to be exposed to infectious diseases compared to the general population. For this reason, according to the National Immunization and Prevention Plan, all HCWs should have demonstrable evidence of immunity to measles, mumps, rubella, varicella and Hepatitis B. Earlier studies have already shown that a large percentage of Italian operators lacked immune protection for one or more of those pathogens.The aim of this study was to evaluate the immunization status for vaccine-preventable diseases of HCWs in a large Italian teaching hospital. We retrospectively evaluated clinical records and serological data of HCWs who followed the occupational health surveillance program between January 1 and December 31 2019. We reviewed the clinical records of 1,017 HCWs: 393 males and 624 females with a median age of 35.69 y (range: 19-67). Protective IgG antibody values were documented in the 88.0%, 75.7%, 90.3%, 87.4% and 85.7% of the HCWs screened, respectively, against measles, mumps, rubella, varicella and Hepatitis B. Age was significantly related to serological protection against measles, mumps and varicella but was not significantly related to protective IgG levels for rubella and HBV.Female gender was significantly related to a higher protection rate against Hepatitis B (87.8 vs 82.4%; p < .01) whereas males were significantly more protected against varicella (92-4 vs 84.1%; p < .01).Our study shows suboptimal levels of protection among Italian HCWs and a consequent increased risk of infection for them and their patients. Public health policies should be focused on improving preventive strategies, including serological screening and workplace vaccination of nonimmune individuals.

Recommendations for vaccination in multiple myeloma: a consensus of the European Myeloma Network

Vaccination is one of the most successful medical interventions that has saved the life of millions of people. Vaccination is particularly important in patients with multiple myeloma, who have an increased risk of infections due to the disease-inherent immune suppression, and because of the immune suppressive effects of therapy. Hence, all appropriate measures should be exploited, to elicit an effective immune response to common pathogens like influenza, pneumococci, varicella zoster virus, and to those bacteria and viruses (haemophilus influenzae, meningococci, and hepatitis) that frequently may pose a significant risk to patients with multiple myeloma. Patients after autologous, and specifically after allogeneic transplantation have severely reduced antibody titers, and therefore require a broader spectrum of vaccinations. Response to vaccination in myeloma often is less vigorous than in the general population, mandating either measurement of the postvaccination antibody titers and/or repeating the vaccination. Here, we compile the existing data on vaccination in multiple myeloma and provide recommendations for clinical practice.

Australian mumps serosurvey 2012-2013: any cause for concern?

Objectives

To determine population-level immunity to mumps in Australia.

Methods

We tested randomly selected specimens from people aged 1-49 years using the Enzygnost anti-parotitis IgG enzyme immunoassay from an opportunistically collected serum bank in 2012-2013. Weighted estimates of the proportion seropositive and equivocal for mumps-specific IgG antibody were determined by age group and compared with two previous national serosurveys conducted in 2007-2008 and 1997-1998.

Results

Overall, 82.1% (95% CI 80.6-83.5%) of 2,729 specimens were positive or equivocal for mumps-specific IgG antibodies (71.1% positive [95% CI 69.4-72.9%]; 10.9% equivocal [95% CI 9.8-12.2%]). The proportion positive or equivocal was higher in 2012-2013 (82.1%) than in 2007-2008 (75.5%) and 1997-1998 (72.5%), but varied by age. The proportion positive or equivocal in 2012-2013 was above 80% for all age groups older than 1 year except for 30-34 year olds, corresponding to the 1978-1982 birth cohort previously identified as most likely to have missed out on a second MMR vaccine dose.

Conclusion

Seropositivity to mumps in 2012-2013 was well-maintained compared with previous serosurveys. Low mumps notifications over this period in Australia suggest an absence of community-based transmission of mumps infection in the general population, but recent outbreaks among Aboriginal adolescents and young adults in close-contact settings, despite high 2-dose MMR coverage, suggest that seroprotection may be insufficient in other similar settings in Australia.Seropositivity to mumps in 2012-2013 was well-maintained compared with previous serosurveys. Low mumps notifications over this period in Australia suggest an absence of community-based transmission of mumps infection in the general population, but recent outbreaks among Aboriginal adolescents and young adults in close-contact settings, despite high 2-dose MMR coverage, suggest that seroprotection may be insufficient in other similar settings in Australia.

The variability of the serological response to SARS-corona virus-2: Potential resolution of ambiguity through determination of avidity (functional affinity)

Data on the serological response toward severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) in 16 recent reports were analyzed and a high degree of variability was shown. Immunoglobulin M (IgM) responses were either found earlier than IgG, or together with IgG, later than IgG, or were missing. Therefore, clear distinctions between early, intermediate, and past infections are obviously not possible merely on the basis of IgM and IgG determinations. A review of publications on the serology of other virus groups shows that variable IgM responses can be found as well and therefore are not unique for SARS‐CoV‐2 infections. A model to explain this variability is proposed. The inclusion of avidity determination into regular diagnostic procedures has allowed to resolve such “atypical” serological constellations. The potential use of avidity determination for the diagnosis of COVID‐19, for risk assessment, epidemiological studies, analysis of cross reactions, as well as for the control of vaccination programs is suggested and discussed.

The serological response to SARS CoV‐2 infection is highly variable.

The mere detection of specific IgM and IgG does not allow to distinguish between acute and past infection.

The variable IgM and IgG responses after SARS CoV‐2 infection are analogous to serological findings in other virus systems.

Variable IgM and IgG responses can be rationally explained by models that describe immunoglobulin production by the immune system.

Avidity determination of SARS CoV‐2 IgG is suggested for resolution of diagnostic ambiguity.

Does Early Childhood Vaccination Protect Against COVID-19?

The coronavirus disease 2019 (COVID-19) is an on-going pandemic caused by the SARS-coronavirus-2 (SARS-CoV-2) which targets the respiratory system of humans. The published data show that children, unlike adults, are less susceptible to contracting the disease. This article aims at understanding why children constitute a minor group among hospitalized COVID-19 patients. Here, we hypothesize that the measles, mumps, and rubella (MMR) vaccine could provide a broad neutralizing antibody against numbers of diseases, including COVID-19. Our hypothesis is based on the 30 amino acid sequence homology between the SARS-CoV-2 Spike (S) glycoprotein (PDB: 6VSB) of both the measles virus fusion (F1) glycoprotein (PDB: 5YXW_B) and the rubella virus envelope (E1) glycoprotein (PDB: 4ADG_A). Computational analysis of the homologous region detected the sequence as antigenic epitopes in both measles and rubella. Therefore, we believe that humoral immunity, created through the MMR vaccination, provides children with advantageous protection against COVID-19 as well, however, an experimental analysis is required.

Will We Have a Cohort of Healthcare Workers Full Vaccinated against Measles, Mumps, and Rubella?

Healthcare workers are a population exposed to several infectious diseases, and an immunization programme is essential for the maintenance of good vaccination coverage to protect workers and patients. A population of 10,653 students attending degree courses at Padua Medical School (medicine and surgery, dentistry and health professions) was screened for vaccination coverage and antibody titres against rubella, mumps, and measles. The students were subdivided into five age classes according to their date of birth: those born before 1980, between 1980 and 1985, between 1986 and 1990, between 1991 and 1995, and after 1995. Vaccination coverage was very low in students born before 1980, but the rate of positive antibody titre was high due to infection in infancy. Increasing date of birth showed increased vaccination coverage. In contrast, immune coverage was high for rubella (more than 90%) but not for mumps and measles (approximately 80%). An “anomaly” was observed for mumps and measles in the cohort born between 1991 and 1995, probably due to the trivalent vaccine formulation. Students born after 1990 showed vaccination coverage that exceeded 90%. It is therefore very likely that we will have a future generation of healthcare workers with optimal vaccination coverage.

Application of a fast and cost-effective 'three-in-one' MMR ELISA as a tool for surveying anti-MMR humoral immunity: the Hungarian experience

In Hungary, between February 2017 and July 2019, 70 confirmed measles cases were reported, raising questions about the adequacy of population-level immunity. Although the assumed vaccination coverage is ≥99%, in a recent study, we detected potential gaps in the anti-measles humoral immunity. In Hungary, according to a decree by the Ministry of Public Welfare, beginning from 2021, the healthcare provider should conduct a serosurvey of anti-measles protection levels of healthcare professionals. To facilitate the compliance with this requirement, we developed a quick 'three-in-one' or 'triple' MMR (measles, mumps and rubella) indirect ELISA (IgG); an assay format that is currently not available commercially. High throughput applicability of the 'three-in-one' ELISA was verified using 1736 sera from routine laboratory residual samples, using an automated platform (Siemens BEP 2000 Advance). Assay verification was performed by comparing the full antigen repertoire-based 'target' assay with in-house 'control' assays using recombinant viral antigen coatings, and by validated commercially available kits. Indirect immunofluorescence was used as an independent reference method. Data were analysed using OriginLab, IBM SPSS, RStudio and MedCalc. In case of measles, we combined our current results with previously published data (Ntotal measles = 3523). Evaluation of anti-mumps and anti-rubella humoral antibody levels was based on the measurement of 1736 samples. The lowest anti-measles seropositivity (79.3%) was detected in sera of individuals vaccinated between 1978 and 1987. Considering the antigen-specific seropositivity ratios of all samples measured, anti-measles, -mumps and -rubella IgG antibody titres were adequate in 89.84%, 91.82% and 92.28%, respectively. Based on the virus-specific herd immunity threshold (HIT) values (HITMeasles = 92-95%, HITMumps = 75-86%, HITRubella = 83-86), it can be stated that regarding anti-measles immunity, certain age clusters of the population may have inadequate levels of humoral immunity. Despite the potential gaps in herd immunity, the use of MMR vaccine remains an effective and low-cost approach for the prevention of measles, mumps and rubella infections.

The effect of time since measles vaccination and age at first dose on measles vaccine effectiveness - A systematic review

BACKGROUND

In settings where measles has been eliminated, vaccine-derived immunity may in theory wane more rapidly due to a lack of immune boosting by circulating measles virus. We aimed to assess whether measles vaccine effectiveness (VE) waned over time, and if so, whether differentially in measles-eliminated and measles-endemic settings.

METHODS

We performed a systematic literature review of studies that reported VE and time since vaccination with measles-containing vaccine (MCV). We extracted information on case definition (clinical symptoms and/or laboratory diagnosis), method of vaccination status ascertainment (medical record or vaccine registry), as well as any biases which may have arisen from cold chain issues and a lack of an age at first dose of MCV. We then used linear regression to evaluate VE as a function of age at first dose of MCV and time since MCV.

RESULTS

After screening 14,782 citations, we identified three full-text articles from measles-eliminated settings and 33 articles from measles-endemic settings. In elimination settings, two-dose VE estimates increased as age at first dose of MCV increased and decreased as time since MCV increased; however, the small number of studies available limited interpretation. In measles-endemic settings, one-dose VE increased by 1.5% (95% CI 0.5, 2.5) for every month increase in age at first dose of MCV. We found no evidence of waning VE in endemic settings.

CONCLUSIONS

The paucity of data from measles-eliminated settings indicates that additional studies and approaches (such as studies using proxies including laboratory correlates of protection) are needed to answer the question of whether VE in measles-eliminated settings wanes. Age at first dose of MCV was the most important factor in determining VE. More VE studies need to be conducted in elimination settings, and standards should be developed for information collected and reported in such studies.

Assessment of immune status against measles, mumps, and rubella in young Kuwaitis: MMR vaccine efficacy

Seroprevalence studies on measles, mumps, and rubella immunoglobulin G (IgG) antibodies after the implementation of the measles-mumps-rubella (MMR) vaccine are lacking in Kuwait. This study is an age-stratified serological study to assess the herd immunity to measles, mumps, and rubella among the young Kuwaiti population to evaluate the effectiveness of the MMR vaccine. IgG antibody titers to mumps, measles, and rubella were determined with commercial immune-assay in serum samples of 1000 Kuwaitis aged 5 to 20 years. The highest level of seropositivity was to measles (94.6%), which was significantly higher in females than in males. The highest seronegativity was for mumps (29%). The percentage of the young Kuwaiti population who were serologically positive for all the components of the MMR vaccine was 47%, and 2% of the individuals were without any protective antibodies to measles, mumps, and rubella. Females aged 5 to 10 years were best protected to rubella; however, seronegativity in 8.2% of 11- to 20-year-old females makes them vulnerable to rubella virus infection and congenital complications during pregnancy. The study provided insight into the effect of the MMR vaccine on seroprevalence of antibodies against measles, mumps, and rubella in Kuwait, which will contribute to the global knowledge base of vaccine coverage and help to inform elimination strategies. The findings strengthen the need for a third dose of MMR vaccine and catch-up campaigns for the young Kuwaiti population to increase vaccination coverage and prevent waning immunity, especially among those who received only one dose of the vaccine during childhood.