Predictors of SARS-CoV-2 seropositivity prior to COVID-19 vaccination among children 0-4 years and their household members in the SEARCh Study

Background

Estimates of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) seroprevalence in young children and risk factors for seropositivity are scarce. Using data from a prospective cohort study of households during the pre-coronavirus disease 2019 (COVID-19) vaccine period, we estimated SARS-CoV-2 seroprevalence by age and evaluated risk factors for SARS-CoV-2 seropositivity.

Methods

The SARS-CoV-2 Epidemiology and Response in Children (SEARCh) study enrolled 175 Maryland households (690 participants) with ≥1 child aged 0–4 years during November 2020–March 2021; individuals vaccinated against COVID-19 were ineligible. At enrollment, participants completed questionnaires about sociodemographic and health status and work, school, and daycare attendance. Participants were tested for SARS-CoV-2 antibodies in sera. Logistic regression models with generalized estimating equations (GEE) to account for correlation within households assessed predictors of individual- and household-level SARS-CoV-2 seropositivity.

Results

Of 681 (98.7%) participants with enrollment serology results, 55 (8.1%; 95% confidence interval [CI], 6.3%–10.4%) participants from 21 (12.0%) households were seropositive for SARS-CoV-2. Among seropositive participants, fewer children than adults reported being tested for SARS-CoV-2 infection before enrollment (odds ratio [OR] = 0.23; 95% CI, .06–.73). Seropositivity was similar by age (GEE OR vs 0–4 years: 1.19 for 5–17 years, 1.36 for adults; P = .16) and was significantly higher among adults working outside the home (GEE adjusted OR = 2.2; 95% CI, 1.1–4.4) but not among children attending daycare or school.

Conclusions

Before study enrollment, children and adults in this cohort had similar rates of SARS-CoV-2 infection as measured by serology. An adult household member working outside the home increased a household's odds of SARS-CoV-2 infection, whereas a child attending daycare or school in person did not.

Safety and Immunogenicity of the Respiratory Syncytial Virus Vaccine RSV/ΔNS2/Δ1313/I1314L in RSV-Seronegative Children

Background

Respiratory syncytial virus (RSV) is the leading global cause of severe pediatric acute respiratory tract illness, and a vaccine is needed. RSV/ΔNS2/Δ1313/I1314L contains 2 attenuating elements: (1) deletion of the interferon antagonist NS2 gene and (2) deletion of codon 1313 of the RSV polymerase gene and the stabilizing missense mutation I1314L. This live vaccine candidate was temperature-sensitive, genetically stable, replication restricted, and immunogenic in nonhuman primates.

Methods

A single intranasal dose of RSV/ΔNS2/Δ1313/I1314L was evaluated in a double-blind, placebo-controlled trial (vaccine-placebo ratio, 2:1) at 10⁶ plaque-forming units (PFU) in 15 RSV-seropositive children and at 10⁵ and 10⁶ PFU in 21 and 30 RSV-seronegative children, respectively.

Results

In RSV-seronegative children, the 10⁵ PFU dose was overattenuated, but the 10⁶ PFU dose was well tolerated, infectious (RSV/ΔNS2/Δ1313/I1314L replication detected in 90% of vaccinees), and immunogenic (geometric mean serum RSV plaque-reduction neutralizing antibody titer, 1:64). After the RSV season, 9 of 20 vaccinees had increases in the RSV titer that were significantly greater than those in 8 of 10 placebo recipients (1:955 vs 1:69, respectively), indicating that the vaccine primed for anamnestic responses after natural RSV exposure.

Conclusion

Rational design yielded a genetically stable candidate RSV vaccine that is attenuated yet immunogenic in RSV-seronegative children, warranting further evaluation.

Clinical Trials Registration

NCT01893554.

Evaluation of a Live Attenuated Human Metapneumovirus Vaccine in Adults and Children

We conducted a phase I clinical trial of an experimental live attenuated recombinant human metapneumovirus (HMPV) vaccine (rHMPV-Pa) sequentially in adults, HMPV-seropositive children, and HMPV-seronegative children, the target population for vaccination. rHMPV-Pa was appropriately restricted in replication in adults and HMPV-seropositive children but was overattenuated for HMPV-seronegative children.

Evaluation of a Live-Attenuated Human Parainfluenza Type 1 Vaccine in Adults and Children

We conducted a phase I clinical trial (clinicaltrials.gov identifier, NCT00641017) of the experimental live-attenuated human parainfluenza virus type 1 (HPIV-1) vaccine rHPIV-1/84/del 170/942A sequentially in 3 groups: adults, HPIV-1-seropositive children, and HPIV-1-seronegative children, the target population for vaccination. rHPIV-1/84/del 170/942A was appropriately restricted in replication in adults and HPIV-1-seropositive children but was overattenuated (ie, insufficiently infectious and immunogenic) for HPIV-1-seronegative children.