Both vaccines still excel at preventing infection while others only guard against severe disease.

Scientists are still learning about the highly contagious Omicron variant of the COVID-19 virus, which arrived seemingly out of nowhere a few weeks ago and is sweeping across the United States and other countries around the globe.

Here’s what we have learned, however:

  • Omicron is spreading faster than Delta and previous variants, causing major spikes in infections and threatening to overwhelm hospitals.
  • The mRNA vaccines developed by Moderna and Pfizer appear to be the only vaccines in the world that effectively guard against infection by the Omicron variant. However, all vaccines still appear to have some degree of effectiveness in preventing life-threatening illness. Most cases involving hospitalization or death continue to be among those who are not vaccinated.
  • Even the Moderna and Pfizer vaccines tend to lose some of their effectiveness over the course of six months, so health officials strongly recommend booster shots for individuals over the age of 15. Those who had the single-shot J&J vaccine have the option of getting a Moderna or Pfizer booster shot.
  • It is as important as ever to follow recommended safety protocols to limit the spread of the Omicron variant, even if you’ve had your shots. Wear a mask, especially in stores and other indoor spaces, and continue to maintain social distancing. If you feel sick or have been exposed to someone who has tested positive, get tested immediately and do not come to work!
  • Some evidence suggests that Omicron may be less likely than other variants to cause severe illness among otherwise healthy individuals. Nevertheless, even those with no apparent symptoms can spread the virus to vulnerable elders and others with compromised immune systems.

Ask your doctor if you have questions or doubts about taking the vaccine.

CAUTION: The information provided here is tentative and subject to change pending further research and analysis. For current information about the virus or to schedule a vaccine appointment, visit the Arizona Department of Health services website,