Waning Immunity Against Respiratory Syncytial Virus During the Coronavirus Disease 2019 Pandemic.

Health jurisdictions have seen a near-disappearance of respiratory syncytial virus (RSV) during the first year of the coronavirus disease 2019 (COVID-19) pandemic. Over this corresponding period, we report a reduction in RSV antibody levels and live virus neutralization in sera from women of childbearing age and infants between May to June 2020 and February to June 2021, in British Columbia (BC), Canada. This supports that antibody immunity against RSV is relatively short-lived and that maintaining optimal antibody levels in infants requires repeated maternal viral exposure. Waning immunity may explain the interseasonal resurgence of RSV cases observed in BC and other countries.

Efficacy of Palivizumab Immunoprophylaxis for Reducing Severe RSV Outcomes in Children with Immunodeficiencies: A Systematic Review.

BACKGROUND: Palivizumab is recommended for prevention of severe respiratory syncytial virus (RSV) disease in immunocompromised children, despite a lack of strong supporting evidence. The recent approval of substitute RSV-neutralizing monoclonal antibodies against RSV, offers an opportunity to synthesize the most current evidence supporting the palivizumab standard of care. OBJECTIVE: To evaluate the efficacy of palivizumab in preventing acute respiratory tract infection- or RSV-related hospitalization, or mortality in immunocompromised children. METHODS: We searched Ovid MEDLINE and EMBASE for published clinical studies that investigated outcomes of palivizumab use in children. We included clinical trials, cohort studies, and case-control studies. The primary outcomes were RSV-related or respiratory viral infection-related hospitalizations, or RSV-related mortality. This systematic review was registered in PROSPERO (ID CRD42021248619) and is reported in accordance with the PRISMA guidelines. RESULTS: From the 1993 records, six studies were eligible and included, for a total of 625 immunocompromised children with an heterogeneous composition of primary and acquired immunodeficiencies enrolled from palivizumab programs. There were no intervention studies. None of the studies included a control group. RSV hospitalizations were infrequent (0%-3.1% of children). Most children included received palivizumab, although one study (n = 56) did not specify how many received palivizumab. RSV mortality was neither observed, in three studies, nor reported, in three other studies. CONCLUSIONS: The evidence supporting the use of palivizumab for prevention of severe RSV disease in immunocompromised children remains extremely limited and appears insufficient to justify prioritizing this intervention as the current standard of care over alternative interventions.

Bordetella pertussis infection following relaxation of COVID-19 non-pharmaceutical interventions in 2021-2023 in Vancouver metropolitan area, British Columbia, Canada.

BACKGROUND: We recently reported a near disappearance of B. pertussis and a decline in anti-B. pertussis antibodies during the peak implementation of Coronavirus disease 2019 (COVID-19) non-pharmaceutical interventions (NPI) in 2021 in British Columbia (BC), Canada. During 2021-2023, incidence of reported B. pertussis cases remained low in BC at < 1/100,000 population. This study determined how serological evidence of B. pertussis changed after the gradual relaxation of NPI between 2021-2023. METHODS: Randomly selected blood samples from school staff 25-51 years old (n = 65) were collected yearly between 2021-2023 in the Vancouver metropolitan area, BC, Canada, and tested for anti-pertussis toxin (PT) IgG levels. Serological evidence of B. pertussis infection (thereafter "seroconversion") was defined as a quantifiable anti-PT IgG levels in subjects with anti-PT IgG levels below lower limit of quantification in the preceding year or a > 4-fold increase in anti-PT IgG levels between two subsequent years. Samples were also tested for anti-diphtheria toxoid (DT) IgG, and similar seroconversion criteria were applied to exclude seroconversion due to vaccination with tetanus-diphtheria-acellular-pertussis (Tdap). RESULTS: Three subjects met seroconversion criteria for anti-PT IgG between 2021 and 2022 and 9 between 2022 and 2023, yielding a seroconversion rate of 4.6 /100 person-years and 14.9/100 person-years, P = 0.127, respectively. None of the subjects met the criteria for vaccination with Tdap. The geometric mean concentration of anti-PT IgG showed a statistically significant decrease in 2022 compared with 2021, 4.8 IU/mL IU/ml (95 % confidence interval [CI], 3.8-5.9) vs. 6.4 IU/ml (95 % CI, 4.9-8.2; p = 0.001), followed by a statistically significant increase in 2023 compared with 2022 6.5 IU/ml (95 % CI, 4.9-8.5) vs. 4.8 IU/ml (95 % CI, 3.8-5.9; p = 0.0006), respectively. DISCUSSION: Serological evidence of B. pertussis increased between 2022 and 2023 despite low reported cases, which suggests that B. pertussis circulation resumed after relaxing of COVID-19 NPI.

DDIT4L regulates mitochondrial and innate immune activities in early life.

Pattern recognition receptor responses are profoundly attenuated before the third trimester of gestation in the relatively low-oxygen human fetal environment. However, the mechanisms regulating these responses are uncharacterized. Herein, genome-wide transcription and functional metabolic experiments in primary neonatal monocytes linked the negative mTOR regulator DDIT4L to metabolic stress, cellular bioenergetics, and innate immune activity. Using genetically engineered monocytic U937 cells, we confirmed that DDIT4L overexpression altered mitochondrial dynamics, suppressing their activity, and blunted LPS-induced cytokine responses. We also showed that monocyte mitochondrial function is more restrictive in earlier gestation, resembling the phenotype of DDIT4L-overexpressing U937 cells. Gene expression analyses in neonatal granulocytes and lung macrophages in preterm infants confirmed upregulation of the DDIT4L gene in the early postnatal period and also suggested a potential protective role against inflammation-associated chronic neonatal lung disease. Taken together, these data show that DDIT4L regulates mitochondrial activity and provide what we believe to be the first direct evidence for its potential role supressing innate immune activity in myeloid cells during development.

Why has the epidemiology of RSV changed during the COVID-19 pandemic?

The coronavirus disease 2019 (COVID-19) pandemic has drastically perturbed the epidemiology of Respiratory Syncytial Virus (RSV) respiratory tract infections in children. The reasons for this are not clear. In this article, we review the current literature and critically discuss the different theories to explain why the epidemiology of RSV has changed during the COVID-19 pandemic. Proposed mechanisms include decreased viral immunity in vulnerable age groups caused by the prolonged lack of RSV circulation early in the pandemic, potential Severe Acute Respiratory Syndrome Corona Virus 2 (SARS-CoV-2)-induced immune dysregulation, viral interactions between SARS-CoV-2 and RSV, and modifications in health-seeking behaviors as well as heath systems factors. Research in viral genomics and phylogeny, and more robust immunology research is needed to guide RSV prevention and health care resource planning.

Loss of Respiratory Syncytial Virus Antibody Functions During the Peak of the COVID-19 Pandemic Mitigation Measures.

Studies have linked respiratory syncytial virus (RSV) antibody-mediated phagocytosis and complement deposition to severe RSV infection in humans. This study shows waning of these antibody functions in women of childbearing age in 2020-2021 during the implementation of COVID-19 mitigation measures, in absence of RSV circulation. These functions could be explored as correlates of protection against severe RSV disease.

Respiratory syncytial virus epidemiology and clinical severity before and during the COVID-19 pandemic in British Columbia, Canada: a retrospective observational study.

Background: The COVID-19 pandemic has perturbed the seasonality of respiratory syncytial virus (RSV) infections. However, we lack data on how this impacted the severity of paediatric RSV cases. The objective of this study was to describe the clinical severity of RSV cases before, during and after pandemic measures in British Columbia (BC), Canada. Methods: Retrospective study of RSV cases from September 1st, 2017 to May 15th, 2023, with a review of RSV outcomes in children below 18 years old at BC's paediatric hospital. Temporal changes in RSV cases and hospitalisations were quantified using interrupted time series. Findings: BC experienced only 11 RSV cases (from 95,266 tests) between September 2020 and August 2021. This was followed by a resurgence of 9,529 RSV cases (219,566 tests [4.3% positive tests]) in 2021-22 and 8,215 cases (124,449 tests [6.6% positive tests]) in 2022-23, increased compared to 1,750 cases (48,664 tests [3.6% positive tests]) per corresponding yearly period in 2017-20. From September 2017 to May 2023, the median age of children with RSV at BC Children's Hospital increased from 8.7 [IQR: 2.0-26.0] to 19.6 [3.9-43.7] months per yearly period. More children were hospitalised in 2022-23 (n = 360), compared to 2017-20 (n = 168 per period) and 2021-22 (n = 172). However, we detected no increase in hospitalisations or ICU admissions in children born prematurely or with chronic cardiorespiratory conditions. Interpretation: The increased detection of symptomatic RSV cases in older children in 2021-22 and increased RSV-related hospitalisations in 2022-23 suggest a gradual increase in the pool of immunologically vulnerable children due to a prolonged lack of viral exposure. Funding: Government of Canada via its COVID-19 Immunity Task Force.

SARS-CoV-2 cross-sectional seroprevalence study among public school staff in Metro Vancouver after the first Omicron wave in British Columbia, Canada.

OBJECTIVE: To determine the SARS-CoV-2 seroprevalence among school workers within the Greater Vancouver area, British Columbia, Canada, after the first Omicron wave. DESIGN: Cross-sectional study by online questionnaire, with blood serology testing. SETTING: Three main school districts (Vancouver, Richmond and Delta) in the Vancouver metropolitan area. PARTICIPANTS: Active school staff enrolled from January to April 2022, with serology testing between 27 January and 8 April 2022. Seroprevalence estimates were compared with data obtained from Canadian blood donors weighted over the same sampling period, age, sex and postal code distribution. PRIMARY AND SECONDARY OUTCOMES: SARS-CoV-2 nucleocapsid antibody testing results adjusted for test sensitivity and specificity, and regional variation across school districts using Bayesian models. RESULTS: Of 1850 school staff enrolled, 65.8% (1214/1845) reported close contact with a COVID-19 case outside the household. Of those close contacts, 51.5% (625/1214) were a student and 54.9% (666/1214) were a coworker. Cumulative incidence of COVID-19 positive testing by self-reported nucleic acid or rapid antigen testing since the beginning of the pandemic was 15.8% (291/1845). In a representative sample of 1620 school staff who completed serology testing (87.6%), the adjusted seroprevalence was 26.5% (95% CrI 23.9% to 29.3%), compared with 32.4% (95% CrI 30.6% to 34.5%) among 7164 blood donors. CONCLUSION: Despite frequent COVID-19 exposures reported, SARS-CoV-2 seroprevalence among school staff in this setting remained no greater than the community reference group. Results are consistent with the premise that many infections were acquired outside the school setting, even with Omicron.

Correlates of Protection Against Respiratory Syncytial Virus Infection in Infancy.

The highest morbidity and mortality from respiratory syncytial virus (RSV) infection occurs in young infants. Immunization of expectant mothers during pregnancy has the potential to substantially reduce the burden of RSV disease in a majority of infants. Correlates of protection (COP) are important in guiding the development of maternal RSV vaccines and the design of maternal RSV vaccine trials, as immune response to candidate vaccines should mirror protective RSV immunity at birth. Here, we review the literature reporting correlations between RSV immune measures at birth and clinical RSV outcomes during infancy. Less than a dozen studies have investigated immunological COP with RSV disease or related hospitalization, yielding inconsistent findings overall. The differences in findings between studies could be due to differences in inclusion/exclusion criteria (e.g., the inclusion of older infants who may benefit less from maternal antibodies or infants followed during inter-seasonal periods where RSV is absent), differences in semi-quantitative RSV antibody neutralization assays, or differences in RSV outcome measures such as the sensititivity/specificity of diagnostic tests. Future research in this field should seek to standardize RSV immunological measures and outcomes, expand the breadth of functional RSV measures beyond antibody neutralization, and consider infants' age and seasonality of RSV infection.

Decay of anti-Bordetella pertussis antibodies in women of childbearing age following COVID-19 non-pharmaceutical measures.

BACKGROUND: Immunization against Bordetella pertussis during pregnancy reduces morbidity from severe pertussis in young infants via trans-placental transfer of anti-B. pertussis Immunoglobulin G (IgG). Studies have reported a near disappearance of respiratory pathogens including B. pertussis following implementation of mitigation strategies to control Coronavirus disease 2019 (COVID-19). We explored how immunity against B. pertussis changed in women of childbearing-age through the COVID-19 pandemic. METHODS: Paired blood samples from females of childbearing-age collected at the beginning (May-June 2020) and nearly one year into the COVID-19 pandemic (February-May 2021) in British Columbia (BC), Canada were tested for anti-B. pertussis IgG levels. To ascertain whether early-pandemic IgG levels in 2020 reflected levels in pregnant women early in gestation, 1st trimester sera collected from age-matched healthy pregnant women in 2018 and 2019 were tested for anti-B. pertussis IgG. Levels were compared by t tests. P-value of 0.05 was assigned and statistical significance was set as p < 0.016 using Bonferroni correction. RESULTS: Annual provincial B. pertussis incidences per 100,000 in BC in 2020 (3/100,000) and 2021 (<1/100,000) approximated the lowest levels since 1990. In 2021 vs. 2020, anti-pertussis toxin (PT), filamentous hemagglutinin (FHA) and pertactin (PRN) IgG levels declined in women of childbearing-age: 6.8 IU/ml (95 %CI, 4.2-10.9) vs. 8.4 IU/ml (5.1-13.9; p = 0.004); 18.8 IU/ml (10.9-32.2) vs. 23.6 IU/ml (13.2-42.1; p < 0.001); and 37.1 IU/ml (18.1-75.9) vs. 47.2 IU/ml (24.8-89.9; p = 0.092), respectively. Although all values were slightly higher, anti-PT, FHA and PRN IgG levels in women of childbearing age did not significantly differ in 2020 compared with early-gestation pregnant women in 2018-2019, 8.4 IU/ml (95% CI, 5.1-13.9) vs. 5.4 IU/ml (95% CI, 3.8-7.7; p = 0.166), 23.6 IU/ml (95% CI, 13.2-42.1) vs. 20.1 IU/ml (95% CI, 13.4-30.2; p = 0.656), and 47.2 IU/ml (24.8-89.9) vs. 17.3 IU/ml (95% CI, 10.5-28.7; p = 0.021), respectively. DISCUSSION: B. pertussis infections should be closely monitored during the relaxing of mitigation measures for COVID-19.

SARS-CoV-2 seroprevalence among Vancouver public school staff in British Columbia, Canada: a cross-sectional study.

OBJECTIVES: Few studies reported COVID-19 cases in schools during the 2020/21 academic year in a setting of uninterrupted in-person schooling. The main objective was to determine the SARS-CoV-2 seroprevalence among school staff in Vancouver public schools. DESIGN: Cumulative incident COVID-19 cases among all students and school staff based on public health data, with an embedded cross-sectional serosurvey among a school staff sample that was compared to period, age, sex and geographical location-weighted data from blood donors. SETTING: Vancouver School District (British Columbia, Canada) from kindergarten to grade 12. PARTICIPANTS: Active school staff enrolled from 3 February to 23 April 2021 with serology testing from 10 February to 15 May 2021. MAIN OUTCOME MEASURES: SARS-CoV-2 seroprevalence among school staff, based on spike (S)-based (unvaccinated staff) or N-based serology testing (vaccinated staff). RESULTS: Public health data showed the cumulative incidence of COVID-19 among students attending in-person was 9.8 per 1000 students (n=47 280), and 13 per 1000 among school staff (n=7071). In a representative sample of 1689 school staff, 78.2% had classroom responsibilities, and spent a median of 17.6 hours in class per week (IQR: 5.0-25 hours). Although 21.5% (363/1686) of surveyed staff self-reported close contact with a COVID-19 case outside of their household (16.5% contacts were school-based), 5 cases likely acquired the infection at school based on viral testing. Sensitivity/Specificity-adjusted seroprevalence in 1556/1689 staff (92.1%) was 2.3% (95% CI: 1.6% to 3.2%), comparable to a sex, age, date and residency area-weighted seroprevalence of 2.6% (95% CI: 2.2% to 3.1%) among 5417 blood donors. CONCLUSION: Seroprevalence among staff was comparable to a reference group of blood donors from the same community. These data show that in-person schooling could be safely maintained during the 2020/21 school year with mitigation measures, in a large school district in Vancouver, Canada.