Harvard University on Thursday warned students and staff that the highly infectious omicron coronavirus variant is “likely already present in COVID-19 cases” being diagnosed on campus. Lawrence Bacow, president of the prestigious university, and other leaders wrote a statement advising their community to take all possible steps to reduce their risk of contracting or transmitting the variant. “Our preliminary analysis indicates the omicron variant is likely already present in COVID-19 cases we are seeing on campus,” the university officials wrote. Earlier this week, Harvard announced a “concerning increase” in COVID-19 cases on campus. Officials on Tuesday reported 178 positive cases in the previous seven days, more than three times higher than the average weekly count during the fall semester. The first case of the omicron variant was identified in Massachusetts earlier this month and Boston officials announced the identification of the city’s first three cases on Wednesday. Also Thursday, Harvard announced that all students, faculty, staff and researchers who do not have an approved exemption will be required to obtain a COVID-19 booster shot for the spring semester. “We encourage you to get a booster as soon as possible so you can benefit from the added protection,” administrators wrote. “If you are unable to get a booster before you return to campus following the winter break, additional opportunities will be available, and you will not be barred from entering campus.”