Objective Studies suggest infants may be at increased risk of severe COVID-19 relative to older children, but few data exist regarding the incidence of COVID-19 episodes and associated risk factors. We estimate incidence rates and describe characteristics associated with medically attended COVID-19 episodes among infants younger than 6 months of age. Methods We analyzed electronic medical record data from a cohort of infants born March 1, 2020-February 28, 2021. Data from three health care delivery systems included demographic characteristics, maternal and infant outpatient visit and hospitalization diagnoses, and SARSCoV-2 test results. Medically attended COVID-19 episodes were defined by positive SARSCoV-2 clinical tests and/or COVID-19 diagnosis codes during medical care visits. Unadjusted and site-adjusted incidence rates by infant month of age, low and high SARS-CoV-2 circulation periods and maternal COVID-19 diagnosis were calculated. Results Among 18,192 infants aged <6 months whose mothers received prenatal care within the three systems, 173 (1.0%) had medically attended COVID-19 episodes. Incidence rates were highest among infants aged under 1 month (2.0 per 1,000 person-weeks) and 1 month (2.0 per 1,000 person-weeks) compared with older infants. Incidence rates were also higher for infants born to women with postpartum COVID-19 compared with women without known COVID-19 and women diagnosed with COVID-19 during pregnancy. Conclusion Most medically attended COVID-19 episodes in infants aged <6 months were outpatient care encounters. Infants of women with postpartum COVID-19 had a higher risk of medically attended COVID-19 than infants born to mothers who were diagnosed during pregnancy or never diagnosed underscoring the importance of COVID-19 prevention measures for their household members and caregivers to prevent infections in infants. Copyright The copyright holder for this preprint is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. This article is a US Government work. It is not subject to copyright under 17 USC 105 and is also made available for use under a CC0 license.

Background: Pregnant individuals are at increased risk of coronavirus disease 2019 (COVID-19) hospitalization and death, and primary and booster COVID-19 vaccination is recommended for this population. Method(s): Among a cohort of pregnant individuals who received prenatal care at 3 healthcare systems in the United States, we estimated the cumulative incidence of hospitalization with symptomatic COVID-19 illness. We also identified factors associated with COVID-19 hospitalization using a multivariable Cox proportional hazards model with pregnancy weeks as the timescale and a time-varying adjustor that accounted for severe acute respiratory syndrome coronavirus 2 circulation; model covariates included site, age, race, ethnicity, insurance status, prepregnancy weight status, and selected underlying medical conditions. Data were collected primarily through medical record extraction. Result(s): Among 19 456 pregnant individuals with an estimated due date during 1 March 2020-28 February 2021, 75 (0.4%) were hospitalized with symptomatic COVID-19. Factors associated with hospitalization for symptomatic COVID-19 were Hispanic ethnicity (adjusted hazard ratio [aHR], 2.7 [95% confidence interval {CI}, 1.3-5.5]), Native Hawaiian or Pacific Islander race (aHR, 12 [95% CI, 3.2-45.5]), age <25 years (aHR, 3.1 [95% CI, 1.3-7.6]), prepregnancy obesity (aHR, 2.1 [95% CI, 1.1-3.9]), diagnosis of a metabolic disorder (aHR, 2.2 [95% CI, 1.2-3.8]), lung disease excluding asthma (aHR, 49 [95% CI, 28-84]), and cardiovascular disease (aHR, 2.6 [95% CI, 1.5-4.7]). Conclusion(s): Although hospitalization with symptomatic COVID-19 was uncommon, pregnant individuals should be aware of risk factors associated with severe illness when considering COVID-19 vaccination. Copyright © 2022 Published by Oxford University Press on behalf of Infectious Diseases Society of America. This work is written by (a) US Government employee(s) and is in the public domain in the US.

BACKGROUND: Studies suggest infants may be at increased risk of severe coronavirus disease 2019 (COVID-19) relative to older children, but few data exist regarding the incidence of COVID-19 episodes and associated risk factors. We estimate incidence rates and describe characteristics associated with medically attended COVID-19 episodes among infants younger than 6 months of age. METHODS: We analyzed electronic medical record data from a cohort of infants born March 1, 2020-February 28, 2021. Data from 3 health care delivery systems included demographic characteristics, maternal and infant outpatient visit and hospitalization diagnoses and severe acute respiratory syndrome coronavirus syndrome 2 (SARS-CoV-2) test results. Medically attended COVID-19 episodes were defined by positive SARS-CoV-2 clinical tests and/or COVID-19 diagnosis codes during medical care visits. Unadjusted and site-adjusted incidence rates by infant month of age, low and high SARS-CoV-2 circulation periods and maternal COVID-19 diagnosis were calculated. RESULTS: Among 18,192 infants <6 months of age whose mothers received prenatal care within the 3 systems, 173 (1.0%) had medically attended COVID-19 episodes. Incidence rates were highest among infants under 1 month of age (2.0 per 1000 person-weeks) and 1 month (2.0 per 1000 person-weeks) compared with older infants. Incidence rates were also higher for infants born to women with postpartum COVID-19 compared with women without known COVID-19 and women diagnosed with COVID-19 during pregnancy. CONCLUSIONS: Infants of women with postpartum COVID-19 had a higher risk of medically attended COVID-19 than infants born to mothers who were diagnosed during pregnancy or never diagnosed underscoring the importance of COVID-19 prevention measures for their household members and caregivers to prevent infections in infants.

Influenza testing and case-confirmation rates in pregnant populations have not been reported during the coronavirus disease 2019 (COVID-19) pandemic. Using electronic medical record data from a cohort of nearly 20,000 pregnancies in the United States, this retrospective cohort study examines the frequency of acute respiratory or febrile illness encounters, influenza testing, and influenza positivity during the 2020-2021 influenza season, which occurred during the COVID-19 pandemic, compared with the 2019-2020 influenza season, which largely did not. The ratios of influenza tests to acute respiratory or febrile illness visits were similar in the 2019-2020 and 2020-2021 influenza seasons (approximately 1:8 and 1:9, respectively) but were low and varied by study site. Although influenza testing in pregnant patients continued in the 2020-2021 season, when severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) circulation was widespread in the United States, no cases of influenza were identified in our study cohort.

BACKGROUND: Identifying SARS-CoV-2 infections during peripartum hospitalizations is important to guide care, implement prevention measures, and understand infection burden. METHODS: This cross-sectional analysis used electronic health record data from hospitalizations during which pregnancies ended (peripartum hospitalizations) among a cohort of pregnant persons at 3 U.S. integrated healthcare networks (Sites 1-3). Maternal demographic, medical encounter, SARS-CoV-2 testing, and pregnancy and neonatal outcome information was extracted for persons with estimated delivery and pregnancy end dates during March 2020-February 2021 and ≥1 prenatal care record. Site-stratified multivariable logistic regression was used to identify factors associated with testing and compare pregnancy and neonatal outcomes among persons tested. RESULTS: Among 17,858 pregnant persons, 10,863 (60.8%) had peripartum SARS-CoV-2 testing; 222/10,683 (2.0%) had positive results. Testing prevalence varied by site and was lower during March-May 2020. Factors associated with higher peripartum SARS-CoV-2 testing odds were Asian race (adjusted odds ratio [aOR]: 1.36; 95% CI: 1.03-1.79; referent: White) (Site 1), Hispanic or Latina ethnicity (aOR: 1.33; 95% CI: 1.08-1.64) (Site 2), peripartum Medicaid coverage (aOR: 1.33; 95% CI: 1.06-1.66) (Site 1), and preterm hospitalization (aOR: 1.69; 95% CI: 1.19-2.39 [Site 1]; aOR: 1.39; 95% CI: 1.03-1.88 [Site 2]). CONCLUSIONS: Findings highlight potential disparities in SARS-CoV-2 peripartum testing by demographic and pregnancy characteristics. Testing practice variations should be considered when interpreting studies relying on convenience samples of pregnant persons testing positive for SARS-CoV-2. Efforts to address testing differences between groups could improve equitable testing practices and care for pregnant persons with SARS-CoV-2 infections.

We conducted a cross-sectional study of pregnant women with acute respiratory illness during delivery hospitalizations in influenza season to describe clinical testing for respiratory viruses and infection prevention practices. Women had nasal swabs tested for influenza and other respiratory viruses. Among 91 enrolled women, 22 (24%) had clinical testing for influenza. Based on clinical and study testing combined, 41/91 (45%) women had samples positive for respiratory viruses. The most common virus was influenza (17/91, 19%); 53% (9/17) of influenza virus infections were identified through study testing alone. Only 16% of women were on droplet precautions. Peripartum respiratory infections may be underrecognized.

OBJECTIVE: Despite recommendations by professional organizations that all pregnant women receive inactivated influenza vaccine, safety concerns remain a barrier. Our objective was to assess the effect of trivalent influenza vaccines (IIV3) during pregnancy on parent report 6-month infant development. METHODS: We conducted a multi-site prospective birth cohort study during the 2010-2011 influenza season and followed pregnant women and their newborns through 6 months of age. Information on IIV3 during pregnancy was ascertained from the EHR and self-report. The Ages and Stages Questionnaire-3 (ASQ-3) was completed by the mother to assess 6-month infant neurodevelopment in five domains (communication, gross motor, fine motor, problem-solving, and personal adaptive skills). Scores for each domain above the cut-off point indicating typical development were categorized as "on schedule" while scores in the zones indicating the need for either monitoring or further assessment were categorized as "not on schedule". Multivariable logistic regression was conducted. RESULTS: Of the 1225 infant-mother pairs, 65% received IIV3 during pregnancy. In bivariate analysis, infants of women who received IIV3 during pregnancy were moderately-less likely to need monitoring or further assessment in the personal social domain compared with infants of unvaccinated women (10.0% vs. 14.1%, p = 0.033; crude OR (cOR): 0.68(95%CI:0.48,0.97)). However, after controlling for potential confounders, the findings were no longer statistically significant (aOR:0.72,95%CI: 0.49,1.06,p = 0.46). No significant unadjusted or adjusted associations emerged in any other ASQ-3 domain. CONCLUSION: There was no significant association between IIV3 exposure during pregnancy and 6-month infant development. Studies of IIV3 during pregnancy to assess longer-term developmental outcomes are indicated.

BACKGROUND: This report describes the results of recruitment efforts and the subsequent participation of pregnant women in study activities in a 2010-2012 observational study focused on influenza illness and vaccination in California and Oregon, USA. METHODS: Socio-demographic and health characteristics extracted from electronic medical records were compared among pregnant women who enrolled in the study, refused to participate, or were never reached for study invitation. These characteristics plus additional self-reported information were compared between women who enrolled in two study tracks: a prospective cohort vs. women enrolled following an acute respiratory illness (ARI) medical encounter. The characteristics of women who participated in weekly ARI surveillance (cohort enrollees, year one) and a 6-month follow-up interview (all enrollees) were also examined. RESULTS: In year one, we reached 51% (6938/13,655) of the potential participants we tried to contact by telephone, and 20% (1374/6938) of the women we invited agreed to join the prospective cohort. Women with chronic medical conditions, pregnancy complications, and medical encounters for ARI (prior to pregnancy or during the study period) were more likely to be reached for recruitment and more likely to enroll in the cohort. Twenty percent of cohort enrollees never started weekly surveillance reports; among those who did, reports were completed for 55% of the surveillance weeks. Receipt of the influenza vaccine was higher among women who joined the cohort (76%) than those who refused (56%) or were never reached (54%). In contrast, vaccine uptake among medical enrollees in year one (54%; 53/98) and two (52%; 79/151) was similar to other pregnant women in those years. Study site, white race, non-Hispanic ethnicity, and not having a child aged < 13 years at home were most consistently associated with joining as a cohort or medical enrollee and completing study activities after joining. CONCLUSIONS: We observed systematic differences in socio-demographic and health characteristics across different levels of participant engagement and between cohort and medical enrollees. More methodological research and innovation in conducting prospective observational studies in this population are needed, especially when extended participant engagement and ongoing surveillance are required.

BACKGROUND: We evaluated the feasibility of asking pregnant women to self-collect and ship respiratory specimens. METHODS: In a preliminary laboratory study, we compared the RT-PCR cycle threshold (CT) values of influenza A and B viruses incubated at 4 storage temperatures (from 4-35 degrees C) for 6 time periods (8, 24, 48, 72, and 168 hours and 30-days), resulting in 24 conditions that were compared to an aliquot tested after standard freezing (-20 degrees C) (baseline condition). In a subsequent pilot study, during January-February, 2014, we delivered respiratory specimen collection kits to 53 pregnant women with a medically attended acute respiratory illness using three delivery methods. RESULTS: CT values were stable after storage at temperatures <27 degrees C for up to 72 hours for influenza A viruses and 48 hours for influenza B viruses. Of 53 women who received kits during the pilot, 89% collected and shipped nasal swabs as requested. However, 30% (14/47) of the women took over 2 days to collect and ship their specimen. The human control gene, ribonuclease P (RNase P), was detected in 100% of nasal swab specimens. However, the mean CT values for RNase P (26.5, 95% confidence interval [CI] = 26.0-27.1) and for the 8 influenza A virus positives in our pilot (32.2, 95% CI = 28.9-35.5) were significantly higher than the CTs observed in our 2010-12 study using staff-collected nasal pharyngeal swabs (p-values < .01). DISCUSSION: Self-collection of respiratory specimens is a promising research method, but further research is needed to quantify the sensitivity and specificity of the approach.

OBJECTIVE: To identify characteristics of influenza illness contrasted with non-influenza acute respiratory illnesses (ARI) in pregnant women. STUDY DESIGN: ARI among pregnant women was identified through daily surveillance during two influenza seasons (2010-12). Within 8 days of illness onset, nasopharyngeal swabs were collected, and an interview was conducted for symptoms and other characteristics. A follow-up telephone interview was conducted 1-2 weeks later, and medical records were extracted. Severity of illness was evaluated by self-assessment of 12 illness symptoms, subjective ratings of overall impairment, highest reported temperature, illness duration, and medical utilization. RESULTS: Of 292 pregnant women with ARI, 100 tested positive for influenza viruses. Women with influenza illnesses reported higher symptom severity than those with non-influenza ARI (median score: 18 vs. 16 out of 36; p<.05) and were more likely to report severe subjective feverishness (18% vs. 5%; p<.001), myalgia (28% vs 14%; p<.005), cough (46% vs 30%; p<.01), and chills (25% vs. 13%; p<.01). More influenza illnesses were associated with fever >38.9oC (20% vs. 5%; p<.001) and higher subjective impairment (mean score 5.9 vs. 4.8; p<.001). Differences in overall symptom severity, fever, cough, chills, early healthcare-seeking behavior, and impairment remained significant in multivariate models after adjusting for study site, season, age, vaccination status, and number of days since illness onset. CONCLUSION: Influenza had a greater negative impact on pregnant women than non-influenza ARIs, as indicated by symptom severity and greater likelihood of elevated temperature. These results highlight the importance of preventing and treating influenza illnesses in pregnant women.

BACKGROUND: Although vaccination with trivalent inactivated influenza vaccine (TIV) is recommended for all pregnant women, no vaccine effectiveness (VE) studies of TIV in pregnant women have assessed laboratory-confirmed influenza outcomes. METHODS: We conducted a case-control study over two influenza seasons (2010-2011 and 2011-2012) among Kaiser Permanente health plan members in two metropolitan areas in California and Oregon. We compared the proportion vaccinated among 100 influenza cases (confirmed by RT-PCR) with the proportions vaccinated among 192 controls with acute respiratory illness (ARI) who tested negative for influenza and 200 controls without ARI (matched by season, site, and trimester). RESULTS: Among influenza cases, 42% were vaccinated during the study season compared to 58% and 63% vaccinated among influenza-negative controls and matched ARI-negative controls, respectively. The adjusted VE (95% confidence interval [CI]) of the current season vaccine against influenza A and B was 44% (5%-67%) using the influenza-negative controls and 53% (24%-72%) using the ARI-negative controls. Receipt of the prior season's vaccine, however, had an effect similar to receipt of the current season's vaccine. As such, vaccination in either or both seasons had statistically similar adjusted VE using influenza-negative controls (VE point estimates range=51%-76%) and ARI-negative controls (48%-76%). CONCLUSIONS: Influenza vaccination reduced the risk of ARI associated with laboratory-confirmed influenza among pregnant women by over one-half, similar to VE observed among all adults during these seasons.