Effectiveness of Covid-19 Vaccines in Ambulatory and Inpatient Care Settings

Abstract

Background There are limited data on the effectiveness of the vaccines against symptomatic coronavirus disease 2019 (Covid-19) currently authorized in the United States with respect to hospitalization, admission to an intensive care unit (ICU), or ambulatory care in an emergency department or urgent care clinic. Methods We conducted a study involving adults (≥50 years of age) with Covid-19–like illness who underwent molecular testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We assessed 41,552 admissions to 187 hospitals and 21,522 visits to 221 emergency departments or urgent care clinics during the period from January 1 through June 22, 2021, in multiple states. The patients’ vaccination status was documented in electronic health records and immunization registries. We used a test-negative design to estimate vaccine effectiveness by comparing the odds of a positive test for SARS-CoV-2 infection among vaccinated patients with those among unvaccinated patients. Vaccine effectiveness was adjusted with weights based on propensity-for-vaccination scores and according to age, geographic region, calendar time (days from January 1, 2021, to the index date for each medical visit), and local virus circulation. Results The effectiveness of full messenger RNA (mRNA) vaccination (≥14 days after the second dose) was 89% (95% confidence interval [CI], 87 to 91) against laboratory-confirmed SARS-CoV-2 infection leading to hospitalization, 90% (95% CI, 86 to 93) against infection leading to an ICU admission, and 91% (95% CI, 89 to 93) against infection leading to an emergency department or urgent care clinic visit. The effectiveness of full vaccination with respect to a Covid-19–associated hospitalization or emergency department or urgent care clinic visit was similar with the BNT162b2 and mRNA-1273 vaccines and ranged from 81% to 95% among adults 85 years of age or older, persons with chronic medical conditions, and Black or Hispanic adults. The effectiveness of the Ad26.COV2.S vaccine was 68% (95% CI, 50 to 79) against laboratory-confirmed SARS-CoV-2 infection leading to hospitalization and 73% (95% CI, 59 to 82) against infection leading to an emergency department or urgent care clinic visit. Conclusions Covid-19 vaccines in the United States were highly effective against SARS-CoV-2 infection requiring hospitalization, ICU admission, or an emergency department or urgent care clinic visit. This vaccine effectiveness extended to populations that are disproportionately affected by SARS-CoV-2 infection. (Funded by the Centers for Disease Control and Prevention.)

Product-specific COVID-19 vaccine effectiveness against secondary infection in close contacts, Navarre, Spain, April to August 2021

“…The results show a clear effectiveness of the full COVID-19 vaccination with each of the four evaluated vaccine products and highlight some improvement points. Our findings are consistent with previous studies that reported high effectiveness of full COVID-19 vaccination in preventing hospitalisations [ 9 - 11 ] and moderate VE in preventing symptomatic and asymptomatic SARS-CoV-2 infection [ 12 , 13 ]. However, few studies evaluated VE for specific products [ 11 , 14 ].…”

“…Our findings are consistent with previous studies that reported high effectiveness of full COVID-19 vaccination in preventing hospitalisations [ 9 - 11 ] and moderate VE in preventing symptomatic and asymptomatic SARS-CoV-2 infection [ 12 , 13 ]. However, few studies evaluated VE for specific products [ 11 , 14 ].…”

Interim Estimates of COVID-19 Vaccine Effectiveness Against COVID-19–Associated Emergency Department or Urgent Care Clinic Encounters and Hospitalizations Among Adults During SARS-CoV-2 B.1.617.2 (Delta) Variant Predominance — Nine States, June–August 2021

“…gov), and HHS Protects Public Data Hub (https://protect-public.hhs.gov). the months before Delta became predominant (2,4). However, VE against COVID-19 hospitalization among adults aged ≥75 years was significantly lower than that among adults aged <75 years, which had not been observed previously from this data source (4).…”

Factors predicting readmission in patients with COVID-19

“…Also, the possibility of a false negative result in PCR test was reported in previous studies [ 41 ]. At the end, the key point to indirectly avoid readmission is fully vaccination of the patients after recovery from the COVID-19 through approved vaccine as soon as possible [ 44 , 45 ].…”