Browsing by Author "Bozio, Catherine H."

Now showing 1 - 8 of 8
  • Thumbnail Image
    Item
    Effectiveness of 2-Dose Vaccination with mRNA COVID-19 Vaccines Against COVID-19–Associated Hospitalizations Among Immunocompromised Adults — Nine States, January–September 2021
    (CDC, 2021-11) Embi, Peter J.; Levy, Matthew E.; Naleway, Allison L.; Patel, Palak; Gaglani, Manjusha; Natarajan, Karthik; Dascomb, Kristin; Ong, Toan C.; Klein, Nicola P.; Liao, I-Chia; Grannis, Shaun J.; Han, Jungmi; Stenehjem, Edward; Dunne, Margaret M.; Lewis, Ned; Irving, Stephanie A.; Rao, Suchitra; McEvoy, Charlene; Bozio, Catherine H.; Murthy, Kempapura; Dixon, Brian E.; Grisel, Nancy; Yang, Duck-Hye; Goddard, Kristin; Kharbanda, Anupam B.; Reynolds, Sue; Raiyani, Chandni; Fadel, William F.; Arndorfer, Julie; Rowley, Elizabeth A.; Fireman, Bruce; Ferdinands, Jill; Valvi, Nimish R.; Ball, Sarah W.; Zerbo, Ousseny; Griggs, Eric P.; Mitchell, Patrick K.; Porter, Rachael M.; Kiduko, Salome A.; Blanton, Lenee; Zhuang, Yan; Steffens, Andrea; Reese, Sarah E.; Olson, Natalie; Williams, Jeremiah; Dickerson, Monica; McMorrow, Meredith; Schrag, Stephanie J.; Verani, Jennifer R.; Fry, Alicia M.; Azziz-Baumgartner, Eduardo; Barron, Michelle A.; Thompson, Mark G.; DeSilva, Malini B.; Medicine, School of Medicine
    What is already known about this topic? Studies suggest that immunocompromised persons who receive COVID-19 vaccination might not develop high neutralizing antibody titers or be as protected against severe COVID-19 outcomes as are immunocompetent persons. What is added by this report? Effectiveness of mRNA vaccination against laboratory-confirmed COVID-19–associated hospitalization was lower (77%) among immunocompromised adults than among immunocompetent adults (90%). Vaccine effectiveness varied considerably among immunocompromised patient subgroups. What are the implications for public health practice? Immunocompromised persons benefit from COVID-19 mRNA vaccination but are less protected from severe COVID-19 outcomes than are immunocompetent persons. Immunocompromised persons receiving mRNA COVID-19 vaccines should receive 3 doses and a booster, consistent with CDC recommendations, practice nonpharmaceutical interventions, and, if infected, be monitored closely and considered early for proven therapies that can prevent severe outcomes.
  • Thumbnail Image
    Item
    Effectiveness of a Third Dose of mRNA Vaccines Against COVID-19–Associated Emergency Department and Urgent Care Encounters and Hospitalizations Among Adults During Periods of Delta and Omicron Variant Predominance — VISION Network, 10 States, August 2021–January 2022
    (U.S. Department of Health & Human Services, 2022-01-28) Thompson, Mark G.; Natarajan, Karthik; Irving, Stephanie A.; Rowley, Elizabeth A.; Griggs, Eric P.; Gaglani, Manjusha; Klein, Nicola P.; Grannis, Shaun J.; DeSilva, Malini B.; Stenehjem, Edward; Reese, Sarah E.; Dickerson, Monica; Naleway, Allison L.; Han, Jungmi; Konatham, Deepika; McEvoy, Charlene; Rao, Suchitra; Dixon, Brian E.; Dascomb, Kristin; Lewis, Ned; Levy, Matthew E.; Patel, Palak; Liao, I-Chia; Kharbanda, Anupam B.; Barron, Michelle A.; Fadel, William F.; Grisel, Nancy; Goddard, Kristin; Yang, Duck-Hye; Wondimu, Mehiret H.; Murthy, Kempapura; Valvi, Nimish R.; Arndorfer, Julie; Fireman, Bruce; Dunne, Margaret M.; Embi, Peter; Azziz-Baumgartner, Eduardo; Zerbo, Ousseny; Bozio, Catherine H.; Reynolds, Sue; Ferdinands, Jill; Williams, Jeremiah; Link-Gelles, Ruth; Schrag, Stephanie J.; Verani, Jennifer R.; Ball, Sarah; Ong, Toan C.; Family Medicine, School of Medicine
  • Thumbnail Image
    Item
    Effectiveness of COVID-19 Pfizer-BioNTech BNT162b2 mRNA Vaccination in Preventing COVID-19–Associated Emergency Department and Urgent Care Encounters and Hospitalizations Among Nonimmunocompromised Children and Adolescents Aged 5–17 Years — VISION Network, 10 States, April 2021–January 2022
    (Centers for Disease Control and Prevention, 2022-03-04) Klein, Nicola P.; Stockwell, Melissa S.; Demarco, Maria; Gaglani, Manjusha; Kharbanda, Anupam B.; Irving, Stephanie A.; Rao, Suchitra; Grannis, Shaun J.; Dascomb, Kristin; Murthy, Kempapura; Rowley, Elizabeth A.; Dalton, Alexandra F.; DeSilva, Malini B.; Dixon, Brian E.; Natarajan, Karthik; Stenehjem, Edward; Naleway, Allison L.; Lewis, Ned; Ong, Toan C.; Patel, Palak; Konatham, Deepika; Embi, Peter J.; Reese, Sarah E.; Han, Jungmi; Grisel, Nancy; Goddard, Kristin; Barron, Michelle A.; Dickerson, Monica; Liao , I-Chia; Fadel, William F.; Yang, Duck-Hye; Arndorfer, Julie; Fireman, Bruce; Griggs, Eric P.; Valvi, Nimish R.; Hallowell, Carly; Zerbo, Ousseny; Reynolds, Sue; Ferdinands, Jill; Wondimu, Mehiret H.; Williams, Jeremiah; Bozio, Catherine H.; Link-Gelles, Ruth; Azziz-Baumgartner, Eduardo; Schrag, Stephanie J.; Thompson, Mark G.; Verani, Jennifer R.; Family Medicine, School of Medicine
  • Thumbnail Image
    Item
    Effectiveness of Covid-19 Vaccines in Ambulatory and Inpatient Care Settings
    (Massachusetts Medical Society, 2021-10-07) Thompson, Mark G.; Stenehjem, Edward; Grannis, Shaun; Ball, Sarah W.; Naleway, Allison L.; Ong, Toan C.; DeSilva, Malini B.; Natarajan, Karthik; Bozio, Catherine H.; Lewis, Ned; Dascomb, Kristin; Dixon, Brian E.; Birch, Rebecca J.; Irving, Stephanie A.; Rao, Suchitra; Kharbanda, Elyse; Han, Jungmi; Reynolds, Sue; Goddard, Kristin; Grisel, Nancy; Fadel, William F.; Levy, Matthew E.; Ferdinands, Jill; Fireman, Bruce; Arndorfer, Julie; Valvi, Nimish R.; Rowley, Elizabeth A.; Patel, Palak; Zerbo, Ousseny; Griggs, Eric P.; Porter, Rachael M.; Demarco, Maria; Blanton, Lenee; Steffens, Andrea; Zhuang, Yan; Olson, Natalie; Barron, Michelle; Shifflett, Patricia; Schrag, Stephanie J.; Verani, Jennifer R.; Fry, Alicia; Gaglani, Manjusha; Azziz-Baumgartner, Eduardo; Klein, Nicola P.; Family Medicine, School of Medicine
    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. 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.).
  • Thumbnail Image
    Item
    Effectiveness of Homologous and Heterologous COVID-19 Booster Doses Following 1 Ad.26.COV2.S (Janssen [Johnson & Johnson]) Vaccine Dose Against COVID-19-Associated Emergency Department and Urgent Care Encounters and Hospitalizations Among Adults - VISION Network, 10 States, December 2021-March 2022
    (Center for Disease Control, 2022-04-01) Natarajan, Karthik; Prasad, Namrata; Dascomb, Kristin; Irving, Stephanie A.; Yang, Duck-Hye; Gaglani, Manjusha; Klein, Nicola P.; DeSilva, Malini B.; Ong, Toan C.; Grannis, Shaun J.; Stenehjem, Edward; Link-Gelles, Ruth; Rowley, Elizabeth A.; Naleway, Allison L.; Han, Jungmi; Raiyani, Chandni; Vazquez Benitez, Gabriela; Rao, Suchitra; Lewis, Ned; Fadel, William F.; Grisel, Nancy; Griggs, Eric P.; Dunne, Margaret M.; Stockwell, Melissa S.; Mamawala, Mufaddal; McEvoy, Charlene; Barron, Michelle A.; Goddard, Kristin; Valvi, Nimish R.; Arndorfer, Julie; Patel, Palak; Mitchell, Patrick K.; Smith, Michael; Kharbanda, Anupam B.; Fireman, Bruce; Embi, Peter J.; Dickerson, Monica; Davis, Jonathan M.; Zerbo, Ousseny; Dalton, Alexandra F.; Wondimu, Mehiret H.; Azziz-Baumgartner, Eduardo; Bozio, Catherine H.; Reynolds, Sue; Ferdinands, Jill; Williams, Jeremiah; Schrag, Stephanie J.; Verani, Jennifer R.; Ball, Sarah; Thompson, Mark G.; Dixon, Brian E.; Community and Global Health, Richard M. Fairbanks School of Public Health
    CDC recommends that all persons aged ≥18 years receive a single COVID-19 vaccine booster dose ≥2 months after receipt of an Ad.26.COV2.S (Janssen [Johnson & Johnson]) adenovirus vector-based primary series vaccine; a heterologous COVID-19 mRNA vaccine is preferred over a homologous (matching) Janssen vaccine for booster vaccination. This recommendation was made in light of the risks for rare but serious adverse events following receipt of a Janssen vaccine, including thrombosis with thrombocytopenia syndrome and Guillain-Barré syndrome† (1), and clinical trial data indicating similar or higher neutralizing antibody response following heterologous boosting compared with homologous boosting (2). Data on real-world vaccine effectiveness (VE) of different booster strategies following a primary Janssen vaccine dose are limited, particularly during the period of Omicron variant predominance. The VISION Network§ determined real-world VE of 1 Janssen vaccine dose and 2 alternative booster dose strategies: 1) a homologous booster (i.e., 2 Janssen doses) and 2) a heterologous mRNA booster (i.e., 1 Janssen dose/1 mRNA dose). In addition, VE of these booster strategies was compared with VE of a homologous booster following mRNA primary series vaccination (i.e., 3 mRNA doses). The study examined 80,287 emergency department/urgent care (ED/UC) visits¶ and 25,244 hospitalizations across 10 states during December 16, 2021-March 7, 2022, when Omicron was the predominant circulating variant.** VE against laboratory-confirmed COVID-19-associated ED/UC encounters was 24% after 1 Janssen dose, 54% after 2 Janssen doses, 79% after 1 Janssen/1 mRNA dose, and 83% after 3 mRNA doses. VE for the same vaccination strategies against laboratory-confirmed COVID-19-associated hospitalizations were 31%, 67%, 78%, and 90%, respectively. All booster strategies provided higher protection than a single Janssen dose against ED/UC visits and hospitalizations during Omicron variant predominance. Vaccination with 1 Janssen/1 mRNA dose provided higher protection than did 2 Janssen doses against COVID-19-associated ED/UC visits and was comparable to protection provided by 3 mRNA doses during the first 120 days after a booster dose. However, 3 mRNA doses provided higher protection against COVID-19-associated hospitalizations than did other booster strategies during the same time interval since booster dose. All adults who have received mRNA vaccines for their COVID-19 primary series vaccination should receive an mRNA booster dose when eligible. Adults who received a primary Janssen vaccine dose should preferentially receive a heterologous mRNA vaccine booster dose ≥2 months later, or a homologous Janssen vaccine booster dose if mRNA vaccine is contraindicated or unavailable. Further investigation of the durability of protection afforded by different booster strategies is warranted.
  • Thumbnail Image
    Item
    Laboratory-Confirmed COVID-19 Among Adults Hospitalized with COVID-19–Like Illness with Infection-Induced or mRNA Vaccine-Induced SARS-CoV-2 Immunity — Nine States, January–September 2021
    (CDC, 2021-11) Bozio, Catherine H.; Grannis, Shaun J.; Naleway, Allison L.; Ong, Toan C.; Butterfield, Kristen A.; DeSilva, Malini B.; Natarajan, Karthik; Yang, Duck-Hye; Rao, Suchitra; Klein, Nicola P.; Irving, Stephanie A.; Dixon, Brian E.; Dascomb, Kristin; Liao, I.-Chia; Reynolds, Sue; McEvoy, Charlene; Han, Jungmi; Reese, Sarah E.; Lewis, Ned; Fadel, William F.; Grisel, Nancy; Murthy, Kempapura; Ferdinands, Jill; Kharbanda, Anupam B.; Mitchell, Patrick K.; Goddard, Kristin; Embi, Peter J.; Arndorfer, Julie; Raiyani, Chandni; Patel, Palak; Rowley, Elizabeth A.; Fireman, Bruce; Valvi, Nimish R.; Griggs, Eric P.; Levy, Matthew E.; Zerbo, Ousseny; Porter, Rachael M.; Birch, Rebecca J.; Blanton, Lenee; Ball, Sarah W.; Steffens, Andrea; Olson, Natalie; Williams, Jeremiah; Dickerson, Monica; McMorrow, Meredith; Schrag, Stephanie J.; Verani, Jennifer R.; Fry, Alicia M.; Azziz-Baumgartner, Eduardo; Barron, Michelle; Gaglani, Manjusha; Thompson, Mark G.; Stenehjem, Edward; Family Medicine, School of Medicine
    What is already known about this topic? Previous infection with SARS-CoV-2 or COVID-19 vaccination can provide immunity and protection against subsequent SARS-CoV-2 infection and illness. What is added by this report? Among COVID-19–like illness hospitalizations among adults aged ≥18 years whose previous infection or vaccination occurred 90–179 days earlier, the adjusted odds of laboratory-confirmed COVID-19 among unvaccinated adults with previous SARS-CoV-2 infection were 5.49-fold higher than the odds among fully vaccinated recipients of an mRNA COVID-19 vaccine who had no previous documented infection (95% confidence interval = 2.75–10.99). What are the implications for public health practice? All eligible persons should be vaccinated against COVID-19 as soon as possible, including unvaccinated persons previously infected with SARS-CoV-2.
  • Thumbnail Image
    Item
    Waning 2-Dose and 3-Dose Effectiveness of mRNA Vaccines Against COVID-19–Associated Emergency Department and Urgent Care Encounters and Hospitalizations Among Adults During Periods of Delta and Omicron Variant Predominance — VISION Network, 10 States, August 2021–January 2022
    (Center for Disease Control, 2022-02-18) Ferdinands, Jill M.; Rao, Suchitra; Dixon, Brian E.; Mitchell, Patrick K.; DeSilva, Malini B.; Irving, Stephanie A.; Lewis, Ned; Natarajan, Karthik; Stenehjem, Edward; Grannis, Shaun J.; Han, Jungmi; McEvoy, Charlene; Ong, Toan C.; Naleway, Allison L.; Reese, Sarah E.; Embi, Peter J.; Dascomb, Kristin; Klein, Nicola P.; Griggs, Eric P.; Konatham, Deepika; Kharbanda, Anupam B.; Yang, Duck-Hye; Fadel, William F.; Grisel, Nancy; Goddard, Kristin; Patel, Palak; Liao, I-Chia; Birch, Rebecca; Valvi, Nimish R.; Reynolds, Sue; Arndorfer, Julie; Zerbo, Ousseny; Dickerson, Monica; Murthy, Kempapura; Williams, Jeremiah; Bozio, Catherine H.; Blanton, Lenee; Verani, Jennifer R.; Schrag, Stephanie J.; Dalton, Alexandra F.; Wondimu, Mehiret H.; Link-Gelles, Ruth; Azziz-Baumgartner, Eduardo; Barron, Michelle A.; Gaglani, Manjusha; Thompson, Mark G.; Fireman, Bruce; Community and Global Health, Richard M. Fairbanks School of Public Health
    CDC recommends that all persons aged ≥12 years receive a booster dose of COVID-19 mRNA vaccine ≥5 months after completion of a primary mRNA vaccination series and that immunocompromised persons receive a third primary dose.* Waning of vaccine protection after 2 doses of mRNA vaccine has been observed during the period of the SARS-CoV-2 B.1.617.2 (Delta) variant predominance† (1-5), but little is known about durability of protection after 3 doses during periods of Delta or SARS-CoV-2 B.1.1.529 (Omicron) variant predominance. A test-negative case-control study design using data from eight VISION Network sites§ examined vaccine effectiveness (VE) against COVID-19 emergency department/urgent care (ED/UC) visits and hospitalizations among U.S. adults aged ≥18 years at various time points after receipt of a second or third vaccine dose during two periods: Delta variant predominance and Omicron variant predominance (i.e., periods when each variant accounted for ≥50% of sequenced isolates). Persons categorized as having received 3 doses included those who received a third dose in a primary series or a booster dose after a 2 dose primary series (including the reduced-dosage Moderna booster). The VISION Network analyzed 241,204 ED/UC encounters** and 93,408 hospitalizations across 10 states during August 26, 2021-January 22, 2022. VE after receipt of both 2 and 3 doses was lower during the Omicron-predominant than during the Delta-predominant period at all time points evaluated. During both periods, VE after receipt of a third dose was higher than that after a second dose; however, VE waned with increasing time since vaccination. During the Omicron period, VE against ED/UC visits was 87% during the first 2 months after a third dose and decreased to 66% among those vaccinated 4-5 months earlier; VE against hospitalizations was 91% during the first 2 months following a third dose and decreased to 78% ≥4 months after a third dose. For both Delta- and Omicron-predominant periods, VE was generally higher for protection against hospitalizations than against ED/UC visits. All eligible persons should remain up to date with recommended COVID-19 vaccinations to best protect against COVID-19-associated hospitalizations and ED/UC visits.
  • Thumbnail Image
    Item
    Waning of vaccine effectiveness against moderate and severe covid-19 among adults in the US from the VISION network: test negative, case-control study
    (BMJ Publishing, 2022-10-03) Ferdinands, Jill M.; Rao, Suchitra; Dixon, Brian E.; Mitchell, Patrick K.; DeSilva, Malini B.; Irving, Stephanie A.; Lewis, Ned; Natarajan, Karthik; Stenehjem, Edward; Grannis, Shaun J.; Han, Jungmi; McEvoy, Charlene; Ong, Toan C.; Naleway, Allison L.; Reese, Sarah E.; Embi, Peter J.; Dascomb, Kristin; Klein, Nicola P.; Griggs, Eric P.; Liao, I-Chia; Yang, Duck-Hye; Fadel, William F.; Grisel, Nancy; Goddard, Kristin; Patel, Palak; Murthy, Kempapura; Birch, Rebecca; Valvi, Nimish R.; Arndorfer, Julie; Zerbo, Ousseny; Dickerson, Monica; Raiyani, Chandni; Williams, Jeremiah; Bozio, Catherine H.; Blanton, Lenee; Link-Gelles, Ruth; Barron, Michelle A.; Gaglani, Manjusha; Thompson, Mark G.; Fireman, Bruce; Epidemiology, School of Public Health
    Objective: To 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. Design: Test negative case-control study. Setting: Hospitals, emergency departments, and urgent care clinics in 10 US states, 17 January 2021 to 12 July 2022. Participants: 893 461 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 measures: The 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. Results: 45 903 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. Conclusions: Effectiveness 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.