As 2021 comes to a close, cases of the Omicron variant of the coronavirus are doubling every two to four days. Already, it is the dominant strain of the virus in the United States. Omicron has greater transmissibility than previous variants (it is estimated to be two to three times more contagious than Delta) and is showing relative resistance to vaccines. While two doses of a Pfizer or Moderna vaccine provided extremely strong protection against earlier variants, that protection is reduced to about 30 to 35 percent against Omicron.
Still, there are causes for hope: a booster shot raises vaccine effectiveness to 75 or 80 percent, and for those who have received only two shots or have recovered from previous infections, the probability of Omicron causing severe illness, hospitalization, or death seems relatively low so far. Omicron may be able to evade the antibodies that prevent infection from occurring, but it can still be targeted by T cells—the immune cells that destroy already-infected cells—produced by vaccines or earlier infections. This helps explain why so many breakthrough cases have resulted in comparatively mild symptoms. It’s tempting to imagine a future in which COVID-19 becomes endemic in this form: an illness no worse than the common cold or mild flu, something that might be annoying and inconvenient but won’t require ten-day quarantines, the cancelation of travel plans, or widespread disruption of academic calendars and public events. Tempting, but New York Times science journalist Carl Zimmer calls it “wishful thinking” to be dismissive of Omicron or to be certain that all the new data we collect will confirm that this variant will always prove mild.