University-Associated SARS-CoV-2 Omicron BA.2 Infections, Maricopa County, Arizona, USA, 2022

We investigated a university-affiliated cohort of SARS-CoV-2 Omicron BA.2 infections in Arizona, USA. Of 44 cases, 43 were among students; 26 persons were symptomatic, 8 sought medical care, but none were hospitalized. Most (55%) persons had completed a primary vaccine series; 8 received booster vaccines. BA.2 infection was mild in this young cohort.

, but clinical severity of BA.2 is not yet well described. We describe illness severity and clinical outcomes of a 44-person US university-affiliated cohort, comprised predominantly of students, who tested positive for BA.2.
On January 24, 2022, the Maricopa County Department of Public Health (MCDPH), Arizona, USA, was notified of a BA.2 cluster in persons at a university. Cases were identified through routine surveillance by the university-affiliated genomics laboratory (Appendix, https://wwwnc.cdc.gov/EID/article/28/7/22-0470-App1.pdf). MCDPH investigated to describe the epidemiologic and clinical outcomes of the cohort.
We defined a case as a university student or staff member with a SARS-CoV-2 PCR-positive saliva specimen collected during January 3-23 that was tested in the university laboratory and identified as BA.2 by next-generation sequencing. MCDPH and the university distributed electronic questionnaires to all case-patients via text message, email, or both, which is county and university protocol for anyone with SARS-CoV-2 infection (Appendix). MCDPH investigators also conducted telephone interviews with case-patients to collect information on demographics, recent travel, clinical symptoms and outcomes, and vaccination history. We considered a case lost to follow-up if the person could not be contacted by telephone or refused the telephone interview and they did not respond to either electronic questionnaire. We supplemented race/ethnicity (when otherwise unknown), vaccination history, and university clinic visit data by using the Arizona State Immunization Information System and university records.
We defined illness onset as the first date a casepatient experienced any SARS-CoV-2 symptom or the specimen collection date if a person was asymptomatic or lost to follow-up. We categorized vaccination status as unknown or unvaccinated when no documentation of vaccination was available, or a case-patient reported being unvaccinated. We categorized status as completed a primary series when casepatients had documentation of receiving a Food and Drug Administration-authorized or approved vaccination series or a series listed for emergency use by the World Health Organization and considered casepatients boosted when they had documentation of an additional vaccine dose after completing a primary series. We considered a case previously infected if the patient had a SARS-CoV-2-positive PCR or antigen test collected >90 days before BA.2 illness onset in the statewide communicable disease database.
At least 26 (59%) case-patients experienced >1 symptom, most of which were consistent with a viral upper respiratory tract infection, such as sore throat, rhinorrhea and cold-like symptoms, cough, and fever (Table). Only 8 (18%) case-patients sought medical attention from the university clinic <7 days before or after their BA.2-positive specimen collection date, but none were hospitalized, and none died.
Of 44 cases, 24 (55%) completed only the primary vaccine series, 8 (18%) received booster vaccines, 12 (27%) had an unknown or unvaccinated status, and 1 (2%) was previously infected with SARS-CoV-2. Of 32 case-patients who completed a primary series, 16 (50%) received an mRNA vaccine, either Comirnaty (Pfizer-BioNTech, https://www.pfizer.com) or  *Illness onset is defined as the first day of symptom onset or the day of positive specimen collection (if asymptomatic or lost to follow-up). IQR, interquartile range. †Within 7 days before or 7 days after illness onset. ‡Excludes case-patients who received a booster dose of COVID-19 vaccine (n = 8).
The mild illness and outcomes we describe might have been driven by the cohort's age rather than viral characteristics. Because our study involves a univwersity-affiliated cohort, these findings might not be generalizable to more diverse populations. Also, the low telephone interview participation rate prevented collection of close contact information to assess transmission dynamics. In addition, a potential unknown bias in random specimen selection for sequencing could limit the ability to generalize outcomes to this population.
In conclusion, >50% of 44 case-patients in our cohort experienced symptomatic BA.2 infection, but <25% sought medical care, suggesting BA.2 infection in a young population might be mild. In addition, nearly 75% of case-patients completed a primary vaccination series which, in addition to their age, might have contributed to their mild illness. However, data were insufficient to compare if vaccination status affected whether case-patients experienced symptoms or sought medical care. Among persons who completed a primary vaccine series, only 25% received booster vaccines. By March 2022, in alignment with Centers for Disease Control and Prevention recommendations (6), >33% of Maricopa County residents >18 years of age had received a booster dose. However, targeted efforts might be needed to encourage booster vaccines among university students (7).

Electronic Questionnaires
Maricopa County Department of Public Health (MCDPH) electronic questionnaires are sent via text message to all Maricopa County residents with cases of SARS-CoV-2 infection (based on a positive PCR or antigen test) that are reported to the health department with a telephone number. Requested case information in the MCDPH electronic questionnaire includes demographics and living situation (gender, race, and ethnicity; living situation; workplace type); medical comorbidities and COVID-19 vaccination status; illness onset and severity (date of illness onset, if symptomatic; symptoms experienced; whether they required hospitalization or mechanical ventilation); and infection risk factors (prior known contact with someone with SARS-CoV-2 infection; recent travel).
In addition to the MCDPH electronic questionnaire sent to all Maricopa County residents, the university sends a similar electronic questionnaire to university students and staff with SARS-CoV-2 cases. Questions are similar to those in the MCDPH questionnaire, but do not include information about case race/ethnicity, hospitalization status, or workplace type.
Per MCDPH COVID-19 investigations protocol, if a case-patient responded to the MCDPH electronic questionnaire and did not indicate that they live or work in a high-risk or congregate setting (e.g., long-term care facility, correctional facility, etc.), MCDPH and partner investigators would not attempt a telephone interview with the case-patient. In this investigation, MCDPH investigators attempted to contact each university student or staff member with a case of BA.2 infection regardless of whether they responded to the electronic questionnaire.
Questions in the telephone interview did not deviate from those in the questionnaire, but phone interviews might have enabled more complete data collection in the case of a person who both responded to the questionnaire and the telephone interview.

Cohort Travel and Previous International Residence
Forty-three cases (98% of total) were identified in university students, of which 10 (23%) reported domestic or international travel, or both, in the 14 days before illness onset. Of those who traveled, 8 (80%) traveled internationally and 7 (70%) reported travel to the same country.
Median time from travel return to illness onset was 3 (IQR 3-10) days. Additionally, of student