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At nine US hospitals that enrolled children hospitalized with acute respiratory illness (ARI) during 2015-2016 through 2017-2018 influenza seasons, 50% of children with ARI received clinician-initiated testing for influenza and 35% of cases went undiagnosed due to lack of clinician-initiated testing. Marked heterogeneity in testing practice was observed across sites.

ABSTRACTPurpose: Hospitalized patients with an acute respiratory illness (ARI) were compared to determine if demographic characteristics, timing or influenza vaccination biased who received clinical respiratory viral panel (RVP) testing.Methods: 171 enrollees in an influenza vaccine effectiveness study and a sample of non-enrollees (N = 1029) admitted to a community hospital with ARI during December 2015 through April 2016 comprised the study sample. Those who received clinical RVP testing (n = 292) were compared to those who did not by age, sex, influenza vaccination status, and period (pre-peak influenza season vs. peak/post peak influenza season), using Chi square- and t-tests, and logistic regression.Results: Mean age of participants was 70 years, 58% was female and 45% had been vaccinated against influenza in the 2015–2016 season. Those with clinical RVP testing were significantly younger (67 years) than those without RVP (71 years; P < 0.001), but did not differ with respect to sex or vaccination status. The odds of clinical RVP testing were significantly (P = 0.004) related to younger age (< 65 years) (Odds ratio (OR) = 1.51; 95% CI = 1.14–2.00) and to later period (peak/post peak influenza season; OR = 2.64; 95% CI = 1.84–3.79) but were unrelated to influenza vaccination status or the interaction of time and vaccination status.Conclusion: RVP testing was significantly higher among younger hospitalized patients with an ARI and during the peak and post peak influenza periods than earlier in the season, but influenza vaccination status was not a significant factor. Studies that enroll based on clinical RVP testing should account for potential differences by age.

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One to 4 million cases of community-acquired pneumonia (CAP) occur annually in the United States, resulting in 600,000 hospitalizations and 45,000 deaths. Influenza infection facilitates secondary bacterial infections, and influenza vaccination may prevent CAP directly by preventing influenza pneumonia or indirectly by preventing secondary bacterial CAP.

ObjectiveTo estimate the effectiveness of mRNA vaccines against moderate and severe covid-19 in adults by time since second, third, or fourth doses, and by age and immunocompromised status.DesignTest negative case-control study.SettingHospitals, emergency departments, and urgent care clinics in 10 US states, 17 January 2021 to 12 July 2022.Participants893 461 adults (≥18 years) admitted to one of 261 hospitals or to one of 272 emergency department or 119 urgent care centers for covid-like illness tested for SARS-CoV-2.Main outcome measuresThe main outcome was waning of vaccine effectiveness with BNT162b2 (Pfizer-BioNTech) or mRNA-1273 (Moderna) vaccine during the omicron and delta periods, and the period before delta was dominant using logistic regression conditioned on calendar week and geographic area while adjusting for age, race, ethnicity, local virus circulation, immunocompromised status, and likelihood of being vaccinated.Results45 903 people admitted to hospital with covid-19 (cases) were compared with 213 103 people with covid-like illness who tested negative for SARS-CoV-2 (controls), and 103 287 people admitted to emergency department or urgent care with covid-19 (cases) were compared with 531 168 people with covid-like illness who tested negative for SARS-CoV-2. In the omicron period, vaccine effectiveness against covid-19 requiring admission to hospital was 89% (95% confidence interval 88% to 90%) within two months after dose 3 but waned to 66% (63% to 68%) by four to five months. Vaccine effectiveness of three doses against emergency department or urgent care visits was 83% (82% to 84%) initially but waned to 46% (44% to 49%) by four to five months. Waning was evident in all subgroups, including young adults and individuals who were not immunocompromised; although waning was morein people who were immunocompromised. Vaccine effectiveness increased among most groups after a fourth dose in whom this booster was recommended.ConclusionsEffectiveness of mRNA vaccines against moderate and severe covid-19 waned with time after vaccination. The findings support recommendations for a booster dose after a primary series and consideration of additional booster doses.