Nirmatrelvir-ritonavir (Paxlovid), an oral antiviral treatment, is authorized for
adults with mild-to-moderate COVID-19 who are at increased risk for progression to
severe illness. However, real-world evidence on the benefit of Paxlovid, according
to vaccination status, age group, and underlying health conditions, is limited. To
examine the benefit of Paxlovid in adults aged ≥18 years in the United States, a large
electronic health record (EHR) data set (Cosmos
†
) was analyzed to assess the association between receiving a prescription for Paxlovid
and hospitalization with a COVID-19 diagnosis in the ensuing 30 days. A Cox proportional
hazards model was used to estimate this association, adjusted for demographic characteristics,
geographic location, vaccination, previous infection, and number of underlying health
conditions. Among 699,848 adults aged ≥18 years eligible for Paxlovid during April–August
2022, 28.4% received a Paxlovid prescription within 5 days of COVID-19 diagnosis.
Being prescribed Paxlovid was associated with a lower hospitalization rate among the
overall study population (adjusted hazard ratio [aHR] = 0.49), among those who had
received ≥3 mRNA COVID-19 vaccines (aHR = 0.50), and across age groups (18–49 years:
aHR = 0.59; 50–64 years: aHR = 0.40; and ≥65 years: aHR = 0.53). Paxlovid should be
prescribed to eligible adults to reduce the risk of COVID-19–associated hospitalization.
Paxlovid is an oral antiviral medication that received Emergency Use Authorization
by the Food and Drug Administration on December 22, 2021 (
1
), for use in patients with mild-to-moderate COVID-19 at high risk for progression
to severe illness. Eligibility for Paxlovid includes 1) receipt of a positive SARS-CoV-2
test result (including home antigen test), 2) symptoms consistent with mild-to-moderate
COVID-19, 3) symptom onset within the past 5 days, 4) age ≥18 years (or age ≥12 years
and weight ≥40 kg), 5) one or more risk factors for progression to severe COVID-19,
6) no known or suspected severe renal or hepatic impairment, 7) no history of clinically
significant reactions (e.g., toxic epidermal necrolysis or Stevens-Johnson syndrome)
to the active ingredients (nirmatrelvir or ritonavir) or other components of the product,
and 8) no contraindicated medications.
§
A retrospective analysis was performed on patient records included in Cosmos, a data
set that includes EHR information from >160 million persons in U.S. health systems
covered by Epic, a health care software company (https://cosmos.epic.com). Inclusion
criteria comprised 1) diagnosis of COVID-19 or a positive SARS-CoV-2 test result during
April 1–August 31, 2022
¶
; 2) an outpatient encounter (telemedicine, in-person, urgent care, emergency department,
or other)** associated with the COVID-19 diagnosis; 3) at least one previous face-to-face
encounter in Cosmos during the 3 years preceding the COVID-19 diagnosis
††
; 4) age ≥50 years, or ≥18 years with a documented underlying health condition based
on International Classification of Diseases, Tenth Revision (ICD-10) codes or medical
record fields
§§
; 5) not known to be pregnant; and 6) not known to have pharmacologic or medical contraindications
to Paxlovid use.
¶¶
For patients with multiple SARS-CoV-2 infections during the study period, only data
from the first infection were used in the analysis; date of diagnosis (earliest COVID-19
diagnosis code or positive SARS-CoV-2 test result) was used as a proxy for symptom
onset, and Paxlovid receipt was defined as receiving a prescription for Paxlovid during
the 5 days after COVID-19 diagnosis.*** The primary outcome was overnight COVID-19
hospitalization during the 30 days after the date of diagnosis; secondary outcomes
were all-cause hospitalization and acute respiratory illness (ARI)–associated hospitalization.
†††
Association between Paxlovid receipt and subsequent hospitalization was assessed using
a Cox proportional hazards model, including age group, sex, race and ethnicity, social
vulnerability index,
§§§
number of underlying health conditions, U.S. Census Bureau region of residence, previous
COVID-19 infection, and COVID-19 vaccination status.
¶¶¶
In-hospital COVID-19 mortality during an admission commencing during the 30-day follow-up
period was described but not used as an analytic outcome because of concern about
underascertainment. Persons receiving Paxlovid contributed unexposed time until the
prescription date and exposed time after the prescription date; those not receiving
Paxlovid contributed unexposed time. Follow-up time ended when a hospitalization occurred
or at 30 days after diagnosis, whichever came first. To assess possible bias related
to symptom severity at diagnosis, primary analyses were repeated either excluding
telemedicine visits, or excluding patients hospitalized during the 2 days after diagnosis.
This activity was reviewed by CDC and was conducted consistent with applicable federal
law and CDC policy.****
Among 1,713,120 persons aged ≥18 years with a COVID-19 diagnosis during April 1–August
31, 2022, 699,848 (40.9%) met the inclusion criteria, including 198,927 who received
Paxlovid within 5 days after diagnosis and 500,921 who did not (Figure). Among all
persons with COVID-19 who were eligible for Paxlovid, 15.0% had documentation of previous
infection and 68.8% were confirmed to have received ≥2 COVID-19 mRNA vaccine doses.
Overall, 28.4% of eligible persons received Paxlovid. Paxlovid recipients were more
likely to have a telehealth encounter (49.1%) than nonrecipients (18.4%, standardized
mean difference = 0.69). Prevalences of underlying health conditions were similar
among Paxlovid recipients and nonrecipients (Table 1), and 92.4% had at least one
underlying condition. Persons who were immunocompromised
††††
accounted for 9.4% (64,911) of the study population, 30.2% of whom received Paxlovid.
During the 30 days after a COVID-19 diagnosis, 5,229 (0.75%) persons were hospitalized;
3,311 (63.3%) of these hospitalizations occurred among persons aged ≥65 years. Among
the 198,927 Paxlovid recipients, 930 (0.47%) were hospitalized,
§§§§
compared with 4,299 (0.86%) of nonrecipients. Among the 5,229 persons with a COVID-19
hospitalization, 930 (17.8%) received Paxlovid during the 5 days after diagnosis.
Overall, 211 deaths were reported during a COVID-19 hospitalization. Among those who
received Paxlovid, 0.01% (29 of 198,927) died compared with 0.04% (182 of 500,921)
of persons who did not receive Paxlovid.
FIGURE
Identification of patients with COVID-19* who were eligible for treatment with Paxlovid
(nirmatrelvir-ritonavir) — Cosmos,
†
United States, April–September 2022
Abbreviation: NAAT = nucleic acid amplification test.
* Patients were classified as having COVID-19 based on a diagnosis code for COVID-19
or based on a positive SARS-CoV-2 antigen or nucleic acid amplification test. Among
1,713,120 adults aged ≥18 years who met this definition during April 1–August 1, 2022,
930,847 had a diagnosis code only, 159,878 had a positive NAAT result only, 12,874
had a positive antigen test result only, and 609,521 had both a diagnosis code and
positive test result (NAAT or antigen test). Exclusions summarized at each level of
the flow chart are not mutually exclusive.
† Cosmos is an electronic health record dataset that includes information from >160
million persons in U.S. health systems covered by Epic. https://cosmos.epic.com
The figure is a flow chart outlining the identification of patient records in the
Cosmos data set that were used to examine the association between receiving a Paxlovid
(nirmatrelvir-ritonavir) prescription within 5 days of COVID-19 diagnosis and COVID-19–associated
hospitalization within 30 days in the United States during April–September 2022.
TABLE 1
Characteristics of persons eligible for Paxlovid (nirmatrelvir-ritonavir) by prescription
receipt within 5 days after COVID-19 diagnosis — Cosmos,* United States, April–September
2022
Characteristic
No. (column %)
Standardized mean difference
Paxlovid prescribed
(n = 198,927)
Paxlovid not prescribed (n = 500,921)
Age group, yrs
18–35
20,543 (10.3)
113,716 (22.7)
−0.34
36–49
36,077 (18.1)
107,373 (21.4)
−0.08
50–64
66,929 (33.7)
147,274 (29.4)
0.09
≥65
75,378 (37.9)
132,558 (26.5)
0.25
Sex
Female
122,921 (61.8)
316,677 (63.2)
−0.03
Male
75,984 (38.2)
184,184 (36.8)
0.03
Race and ethnicity
Black or African American, non-Hispanic
17,141 (8.6)
66,574 (13.3)
−0.15
Hispanic or Latino
12,088 (6.1)
38,487 (7.7)
−0.06
White, non-Hispanic
158,696 (79.8)
368,109 (73.5)
0.15
Other, non-Hispanic
†
11,002 (5.5)
27,751 (5.5)
0.00
Social vulnerability index§
0–0.25 (least vulnerable)
58,144 (29.5)
117,590 (23.7)
0.13
0.25–0.50
52,659 (26.7)
124,118 (25.0)
0.04
0.50–0.75
47,755 (24.2)
127,366 (25.7)
−0.03
0.75–1.00 (most vulnerable)
38,902 (19.7)
126,632 (25.6)
−0.14
U.S. Census Bureau region¶
Northeast
47,737 (24.0)
134,818 (26.9)
−0.07
Midwest
78,925 (39.7)
189,000 (37.7)
0.04
South
51,784 (26.0)
140,818 (28.1)
−0.05
West
20,481 (10.3)
36,285 (7.2)
0.11
Outpatient encounter type**
Telemedicine
97,644 (49.1)
91,916 (18.4)
0.69
In-person
56,793 (28.6)
245,004 (48.9)
−0.43
Urgent care
1,814 (0.9)
9,094 (1.8)
−0.08
Emergency department
19,872 (10.0)
98,359 (19.6)
−0.27
Other
22,804 (11.5)
56,548 (11.3)
0.01
Underlying health conditions††
0
16,159 (8.1)
37,072 (7.4)
0.03
1
49,848 (25.1)
152,179 (30.4)
−0.12
≥2
132,920 (66.8)
311,670 (62.2)
0.10
Immunocompromised§§
No
179,321 (90.1)
455,616 (91.0)
−0.03
Yes
19,606 (9.9)
45,305 (9.0)
0.03
Previous infection¶¶
No
180,373 (90.7)
414,440 (82.7)
0.24
Yes
18,554 (9.3)
86,481 (17.3)
−0.24
Obesity
No
100,035 (50.3)
257,590 (51.4)
−0.02
Yes
98,892 (49.7)
243,331 (48.6)
0.02
Smoker (current or former)
No
119,770 (60.2)
287,747 (57.4)
0.06
Yes
79,157 (39.8)
213,174 (42.6)
−0.06
Diabetes
No
161,177 (81.0)
424,246 (84.7)
−0.10
Yes
37,750 (19.0)
76,675 (15.3)
0.10
COVID-19 vaccination status***
≥3 mRNA doses
119,324 (60.0)
209,614 (41.9)
0.37
2 mRNA doses
36,924 (18.6)
115,444 (23.1)
−0.11
Unvaccinated
30,619 (15.4)
141,931 (28.3)
−0.32
Other
12,060 (6.1)
33,932 (6.8)
−0.03
Month of COVID-19 diagnosis
Apr 2022
10,581 (5.3)
50,116 (10.0)
−0.18
May 2022
36,326 (18.3)
104,105 (20.8)
−0.06
Jun 2022
40,747 (20.5)
104,418 (20.9)
−0.01
Jul 2022
58,961 (29.6)
126,991 (25.4)
0.10
Aug 2022
52,312 (26.3)
115,291 (23.0)
0.08
* Cosmos is an electronic health record dataset that includes information from >160
million persons in U.S. health systems covered by Epic. https://cosmos.epic.com
† Includes American Indian or Alaska Native, Native Hawaiian or other Pacific Islander,
or Asian, or other race.
§
https://www.atsdr.cdc.gov/placeandhealth/svi/index.html
¶
https://www2.census.gov/geo/pdfs/maps-data/maps/reference/us_regdiv.pdf
** Telemedicine included virtual, electronic, and telephone encounters. In-person
included in-person outpatient encounters not in the urgent care or emergency department
setting. Other included all other outpatient encounters which could not be categorized
clearly.
††
https://www.cdc.gov/coronavirus/2019-ncov/hcp/clinical-care/underlyingconditions.html
(Accessed October 24, 2022).
§§ Immunocompromised status was defined using International Classification of Diseases,
Tenth Revision codes (adapted from https://academic.oup.com/cid/article/73/11/e4353/6060064
or immunocompromising medication prescribed in the past 6 months (adapted from https://www.atsjournals.org/doi/10.1513/AnnalsATS.201507-415BC).
¶¶
Previous infection was defined as a COVID-19 diagnosis code or positive COVID-19 nucleic
acid amplification test result or antigen test result >90 days before the current
diagnosis.
*** Vaccination categories included 1) unvaccinated if no COVID-19 vaccine had been
received; 2) 2 mRNA dose-recipients if ≥14 days had elapsed after the second dose
and no subsequent doses had been received or <7 days since receipt of third dose;
3) ≥3 mRNA dose-recipients if ≥7 days had elapsed since receipt of the third dose;
and 4) other recipient if any Janssen (Johnson & Johnson) vaccine, other vaccine,
or 1 mRNA vaccine dose had been received any time before COVID-19 diagnosis.
Paxlovid receipt was associated with protection against hospitalization overall (aHR = 0.49,
95% CI = 0.46–0.53) (Table 2), including among persons who had received ≥3 mRNA vaccine
doses (0.50, 95% CI = 0.45–0.55) and 2 previous mRNA vaccine doses (0.50, 95% CI =
0.42–0.58). Paxlovid receipt was associated with lower hospitalization rates among
persons aged 18–49 years (aHR = 0.59, 95% CI = 0.48–0.71), 50–64 years (0.40, 95%
CI = 0.34–0.48), and ≥65 years (0.53, 95% CI = 0.48–0.58). Among persons aged 18–49
years, Paxlovid receipt was associated with lower hospitalization rates among persons
who had received ≥3 mRNA vaccine doses (aHR = 0.75, 95% CI = 0.53–1.06) and those
with only one underlying health condition (aHR = 0.91, 95% CI = 0.58–1.44), but these
estimates did not reach statistical significance. Estimated protection by Paxlovid
was similar by month of diagnosis. Findings from sensitivity analyses, excluding telemedicine
encounters and patients hospitalized during the first 2 days after diagnosis, also
indicated significant reduction in hospitalization among Paxlovid recipients.
¶¶¶¶
In the analysis of secondary outcomes, among the overall study population, Paxlovid
receipt was associated with a lower rate of all-cause hospitalization (aHR = 0.45,
95% CI = 0.43–0.48) and ARI-associated hospitalization (aHR = 0.48, 95% CI = 0.45–0.51).
TABLE 2
Adjusted hazard ratios for COVID-19–associated hospitalization based on Paxlovid prescription
receipt (exposure) — Cosmos,* United States, April–September 2022
Characteristic
Adjusted HR (95% CI)†
No. of participants
No. hospitalized
Events per 100,000 person-days
Overall
Exposed§
Unexposed§
Total
0.49 (0.46–0.53)
693,084
5,229
25.31
15.88
29.05
COVID-19 vaccination status¶
Vaccinated (≥3 mRNA doses)
0.50 (0.45–0.55)
310,196
2,126
22.98
14.30
27.87
Vaccinated (2 mRNA doses)
0.50 (0.42–0.58)
149,498
1,086
24.37
16.37
26.92
Unvaccinated
0.50 (0.43–0.59)
170,789
1,477
29.05
19.60
31.08
UHC**
0
0.89 (0.58–1.36)
52,592
106
6.73
6.51
6.83
1
0.57 (0.45–0.71)
200,116
503
8.40
6.46
9.03
≥2
0.47 (0.44–0.51)
440,376
4,620
35.29
20.56
41.57
Previous infection
††
No
0.48 (0.44–0.51)
589,147
4,715
26.86
16.12
31.53
Yes
0.76 (0.60–0.98)
103,937
514
16.56
13.54
17.20
Immunocompromised§§
No
0.49 (0.45–0.53)
628,706
3,770
20.09
12.61
23.03
Yes
0.50 (0.44–0.58)
64,378
1,459
77.01
45.99
90.49
Month of COVID-19 diagnosis
Apr 2022
0.54 (0.40–0.71)
60,001
450
25.16
17.77
26.71
May 2022
0.57 (0.48–0.67)
139,062
979
23.61
17.06
25.88
Jun 2022
0.51 (0.43–0.60)
143,706
1,006
23.48
15.02
26.76
Jul 2022
0.46 (0.40–0.53)
184,153
1,432
26.09
15.65
30.94
Aug 2022
0.44 (0.38–0.51)
166,162
1,362
27.52
15.60
32.93
Age group, yrs
18–49
0.59 (0.48–0.71)
275,930
886
10.73
6.99
11.68
50–64
0.40 (0.34–0.48)
211,940
1,032
16.30
7.90
20.10
≥65
0.53 (0.48–0.58)
205,214
3,311
54.56
29.72
68.80
By age group, yrs
18–49
Vaccinated (≥3 mRNA doses)
0.75 (0.53–1.06)
84,054
178
7.07
6.10
7.46
Vaccinated (2 mRNA doses)
0.53 (0.35–0.82)
70,159
198
9.43
6.20
10.16
Unvaccinated
0.54 (0.39–0.76)
97,637
417
14.29
9.09
15.13
1 UHC
0.91 (0.58–1.44)
109,620
157
4.78
4.11
4.91
≥2 UHC
0.54 (0.43–0.67)
166,310
729
14.67
8.35
16.54
50–64
Vaccinated (≥3 mRNA doses)
0.41 (0.30–0.55)
98,699
284
9.61
5.28
12.11
Vaccinated (2 mRNA doses)
0.46 (0.33–0.63)
47,111
265
18.84
10.96
21.89
Unvaccinated
0.38 (0.27–0.53)
45,154
355
26.39
12.43
30.35
No UHC
1.11 (0.46–2.68)
32,519
25
2.56
2.87
2.46
1 UHC
0.30 (0.17–0.55)
53,493
109
6.80
2.45
8.72
≥2 UHC
0.40 (0.33–0.48)
125,928
898
23.91
11.04
30.26
≥65
Vaccinated (≥3 mRNA doses)
0.51 (0.46–0.57)
127,443
1,664
44.02
24.51
57.35
Vaccinated (2 mRNA doses)
0.53 (0.43–0.65)
32,228
623
65.58
36.83
78.59
Unvaccinated
0.58 (0.47–0.72)
27,998
705
85.92
52.75
96.15
No UHC
0.84 (0.51–1.36)
20,073
81
13.50
10.34
15.49
1 UHC
0.63 (0.47–0.85)
37,003
237
21.47
13.66
26.77
≥2 UHC
0.51 (0.47–0.56)
148,138
2,993
68.58
37.33
85.48
Abbreviations: HR = hazard ratio; UHC = underlying health condition.
* Cosmos is an electronic health record dataset that includes information from >160
million persons in U.S. health systems covered by Epic. https://cosmos.epic.com
† 95% CIs that exclude 1 were considered to be statistically significant. Multivariable
models were adjusted for age, sex, race and ethnicity, social vulnerability index,
number of underlying health conditions, U.S. Census Bureau region of residence, previous
infection, and COVID-19 vaccination status, excluding the stratum of interest.
§ Persons receiving Paxlovid contributed unexposed time until the prescription date
and exposed time after the prescription date; those not receiving Paxlovid contributed
unexposed time. Follow-up time ended when a hospitalization occurred or at 30-days
after diagnosis, whichever came first.
¶ Vaccination categories included 1) unvaccinated if no COVID-19 vaccine had been
received; 2) 2 mRNA-dose recipients if ≥14 days had elapsed after the second dose
and no subsequent doses had been received or <7 days since receipt of third dose;
3) ≥3 mRNA-dose recipients if ≥7 days had elapsed since receipt of the third dose;
and 4) other recipient if any Janssen (Johnson & Johnson) vaccine, other vaccine,
or 1 mRNA vaccine dose had been received any time before COVID-19 diagnosis.
** https://www.cdc.gov/coronavirus/2019-ncov/hcp/clinical-care/underlyingconditions.html
(Accessed October 24, 2022).
†† Previous infection was defined as a COVID-19 diagnosis code or positive COVID-19
nucleic acid amplification test result or antigen test result >90 days before the
current diagnosis.
§§ Immunocompromised status was defined using International Classification of Diseases,
Tenth Revision codes (adapted from https://academic.oup.com/cid/article/73/11/e4353/6060064
or immunocompromising medication prescribed during the past 6 months (adapted from
https://www.atsjournals.org/doi/10.1513/AnnalsATS.201507-415BC).
Discussion
In a sample of U.S. COVID-19 patients, many of whom had previous SARS-CoV-2 infection
or were vaccinated against COVID-19, the overall COVID-19 hospitalization rate was
51% lower among those who had received a prescription for Paxlovid for presumed mild-to-moderate
COVID-19, compared with those who did not. Similar benefit was seen among persons
who had received ≥2 COVID-19 mRNA vaccine doses. The initial randomized clinical trial
of Paxlovid, which showed an 89% reduction in severe COVID-19 outcomes, was conducted
in unvaccinated persons with no previous infection during the period preceding Omicron
variant predominance (
2
). This real-word analysis demonstrated that being prescribed Paxlovid is associated
with a substantially reduced hospitalization risk among persons with previous immunity
from infection or vaccination in the setting of the current circulating Omicron subvariants.
These findings parallel those of other studies indicating added protection from Paxlovid
even among persons with previous infection or vaccination (
3
–
8
). Paxlovid conferred stable protection during a period in which multiple Omicron
subvariants predominated in the United States. Protection against different predominant
SARS-CoV-2 subvariants is consistent with Paxlovid’s mechanism of action, which inhibits
a highly conserved viral protease (
9
).
Current guidelines for Paxlovid indicate that persons who are at high risk for progression
to severe COVID-19–associated outcomes should be considered for Paxlovid, with older
age being a predominant risk factor (
10
). A study from Israel among persons with mild-to-moderate COVID-19 found comparable
benefit from Paxlovid against severe outcomes among persons aged ≥65 years but did
not find statistical evidence of protection among younger age groups (
3
). The current analysis adds to overall evidence of protection from Paxlovid by finding
a statistically significant benefit among adults aged 18–64 years, specifically among
adults aged 50–64 years with one or more underlying health condition and those aged
18–49 years with two or more underlying health conditions. Although ascertainment
of deaths was limited to those with a documented death during the COVID-19 hospital
admission, the proportion of persons with in-hospital death was also lower among persons
who received Paxlovid (0.01%) than among those who did not (0.04%).
The findings in this report are subject to at least seven limitations. First, receipt
of a Paxlovid prescription is a proxy for use of Paxlovid. Paxlovid course completion
could not be confirmed, which might bias the results toward the null. Second, dates
of diagnosis or test positivity were used to estimate illness onset but might not
reflect date of symptom onset, or the presence of mild-to-moderate COVID-19 symptoms.
Third, possible inclusion of asymptomatic COVID-19 infection in the nonrecipient comparison
group could bias estimates toward the null. Fourth, participants with mild illness
might be overrepresented among Paxlovid prescription recipients compared with nonrecipients,
given the higher proportion of telemedicine visits, potentially leading to overestimation
of protection from Paxlovid; however, a sensitivity analysis restricted to in-person
encounters showed similar overall results. Fifth, underlying health conditions and
immunocompromise were approximated using ICD-10 codes or medical record fields and
might not capture the exact prevalences of these conditions. Sixth, although available
vaccination information is automatically collected at each encounter, incomplete information
could have limited differences in estimates by vaccination status. Finally, hospitalizations
might be incompletely ascertained in Cosmos; this limitation was mitigated by including
only persons with previous face-to-face encounters, indicating higher likelihood of
hospitalization within a participating health system.
This study demonstrates that Paxlovid provides protection against severe COVID-19–associated
outcomes among persons for whom it is recommended, including those with vaccine-conferred
immunity, and that it is underutilized among eligible persons with COVID-19. In this
analysis, only 28% of eligible persons were prescribed Paxlovid. The ease of oral
administration, short duration of therapy, and lower likelihood for resistance make
Paxlovid a useful antiviral. Reduction in nonsevere outcomes, such as duration, number,
and intensity of COVID-19 symptoms, requires further study. Paxlovid should be offered
to eligible persons to protect against COVID-19 hospitalizations, irrespective of
vaccination status, and especially among groups with the highest risk for severe outcomes,
such as older adults and those with multiple underlying health conditions.
Summary
What is already known about this topic?
Nirmatrelvir-ritonavir (Paxlovid) is an outpatient antiviral medication recommended
for adults with mild-to-moderate COVID-19 who have elevated risk of severe illness.
What is added by this report?
Among U.S. adults diagnosed with COVID-19, including those with previous infection
or vaccination, persons who were prescribed Paxlovid within 5 days of diagnosis had
a 51% lower hospitalization rate within 30 days after diagnosis than those who were
not prescribed Paxlovid.
What are the implications for public health practice?
Paxlovid should be offered to eligible adults irrespective of vaccination status,
especially in groups with the highest risk for severe COVID-19 outcomes, such as older
adults and those with multiple underlying health conditions.