According to data released by Barnard and Columbia, there was a slight increase in COVID-19 cases following the Halloween weekend.

The positivity rate on Columbia’s campus rose to 0.42%, from 0.13% over the Halloween weekend. Meanwhile, on Barnard’s campus, the positivity rate rose to 0.2% from 0.14% the previous week. 

This is paralleled by the city’s reported COVID-19 numbers, which saw an increase from 828 cases citywide to 986 over the weekend. New York state also saw an increase in positivity rates, from 0.015% going into Halloween weekend to 0.024% on November 6. The national positivity rate also rose slightly after the weekend, from on 13.99% October 30 to 14.52% on November 6. 

While the university’s spike in positive COVID-19 tests was small, they may have been the result of increased activities both on and off-campus, including Halloween parties and increased socialization. 

These numbers come at a time when Columbia and Barnard have advised that all students over the age of 18 and living in residence halls are eligible to receive a vaccine booster

The relatively small size of Columbia and Barnard’s increases in positivity rates are likely a result of their strict COVID-19 safety and vaccination policies. In April, Columbia announced that vaccines would be mandatory for all students returning for the fall 2021 semester, although medical and religious exemptions would be respected. Barnard later announced an identical policy. Going into the Halloween weekend, Columbia reported a vaccination rate of 99.9% among students, faculty, researchers, and staff. 

While Barnard and Columbia both saw spikes in COVID-19 cases in the weeks after fall move-in, numbers remained consistently low throughout October, particularly for Barnard, whose positivity had stayed below 0.2% from late September until the Halloween weekend.

As a whole, New York City also holds a remarkably high vaccination rate: 74.9% of all eligible residents have received at least one dose of a COVID-19 vaccine, and 67.9% are fully vaccinated. Similarly, in New York state, 75.3% of eligible residents have received at least one dose, and 67.3% are fully vaccinated. These numbers are noticeably higher than national vaccine rates—68% of all eligible Americans have received at least one dose of a COVID-19 vaccine, and just 58.7% are fully vaccinated. Considering both Columbia and New York’s comparatively small increases in positivity rates after Halloween, their markedly high vaccination rates may be attributed to preventing a spike in cases. 

Going into the Halloween weekend, National Institute of Allergy and Infectious Diseases (NIAID) Director Anthony Fauci advised Americans that COVID-19 case numbers were low enough that it would be safe for children to trick or treat, and told all vaccinated people to enjoy their normal Halloween activities, but advised that festivities be kept outdoors. Fauci also said the US should not “prematurely declare victory over COVID,” citing ballooning COVID-19 numbers among the unvaccinated. 

Additionally, on October 29, the CDC authorized the use of the Pfizer-BioNTech vaccine for children ages five to 11, an age group that likely participated in trick-or-treating and additional Halloween activities. However, as the CDC considers full vaccination status to be achieved two weeks after a patient’s second dose of an mRNA vaccine (such as Pfizer, which is the only vaccine currently available in this age group) none of the children vaccinated after this ruling would have been fully vaccinated by Halloween, leaving them vulnerable to COVID-19 exposure.

Pumpkin mask via Flickr