On-campus COVID-19 measures can't contain Omicron

On-campus COVID-19 measures can’t contain Omicron

A study evaluating Cornell University’s COVID-19 surveillance and vaccination programs during an Omicron variant wave suggests that vaccination protected against severe infection, but that it and other mitigation measures — including mass testing — did not prevent rapid transmission of the virus.

The study, published today in JAMA network is open, describes the results of the university’s SARS-CoV-2 transmission prevention programs implemented after the reopening of the personal education campus in fall 2021. Steps included mandatory vaccination of students, induction of vaccination for staff, and on-campus mask requirements. In addition, isolation and contact tracing were performed within hours of all positive COVID-19 tests.

Vaccination rates were high among students and staff at the University of Ithaca, New York, at 97.9%. From August 26 to December 18, 2021, all 15,503 undergraduate students, 2,873 students, and 2,803 staff members were required to register and participate at least once per week in a free on-campus COVID-19 monitoring test.

Every day, school officials review COVID-19 test results to identify sentinel events and outbreaks and guide disease containment strategies. They also monitored test compliance rates and routinely submitted positive samples for genetic sequencing.

Mostly mild infections, no hospitalization

A total of 480 cases of COVID-19 were identified for quarantine upon entry test from August 23 to September 10 (median, 22.9 per day). From September 12 to November 27, 330 infections were detected (1.9 students and 2.4 employees per day), with a positive rate of 0.1%.

But surveillance results changed dramatically among students after they returned from the 5-day Thanksgiving holiday, with 75 infections (median, 10.7 daily cases; 0.5% positivity rate) from November 28 to December 4, 655 cases from December 5 to 11. (93.6; 2.9% positive), and 1,559 infections from December 12-18 (222.7; 5.7%).

From November 28 to December 31, 2,797 infections were reported among students and staff (average daily cases 82.3; 3.1% positive). Students made up 89.0% of the cases and staff made up the rest.

The vast majority of the infected students and staff (82.2%) had mild illnesses, and none of them were hospitalized. Almost all infections (98.6%) occurred in vaccinated people, and more direct contacts tested positive for COVID-19 during this period than before (22.6%, versus 4.4% from August 23 to November 27).

“It is clear that something has changed in the university environment, as similar outbreaks have not yet been seen in off-campus communities or neighboring counties,” the researchers wrote.

On December 1, whole-genome sequencing of omicron-positive samples identified omicron as the causative agent in one case, followed by 1 on December 2, 2 on December 3, and 4 on December 4. By 11 December, 155 of 174 samples sequenced (89.1%) were Omicron, and the rest were identified as the previously dominant delta variant.

Vaccines vary in most cases

In a sign of Omicron’s rapid spread, university officials limited personal interactions on December 10. On December 14, they banned student gatherings, moved exams online, and implemented exit testing protocol.

While these efforts reduced the numbers of infections among students, the infection rate among those who remained in the city immediately after the Christmas holiday (December 26-31) remained higher than it was before Thanksgiving, with 11.5 student cases per day and 16.0 employee cases, a 4.8% positive rate.

The authors said Cornell’s trial demonstrates that standard public health protocols for COVID-19 were not identical to Omicron.

“While vaccination protected against severe disease, it was not sufficient to prevent rapid spread, even when combined with other public health measures including widespread surveillance testing,” they wrote. “As SARS-CoV-2 continues to adapt, surveillance and case-series studies that look across different populations and environments will be useful in identifying hidden events and guiding actions to mitigate harm.”

2022-05-18 19:48:39

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