WASHINGTON — Researchers say federal government data significantly understated the ravages of COVID-19 in nursing homes last year.

Official numbers from the Centers for Disease Control and Prevention are missing about 12% of COVID cases among nursing home residents and 14% of deaths. That’s according to new estimates published Thursday in the Journal of the American Medical Association, Network Open, by a Harvard researcher and her team.

It translates to thousands of missing data points, suggesting more than 118,300 nursing home residents died of COVID-19 last year, or about 30% of all coronavirus deaths nationally.

The researchers attributed the data holes to the federal Centers for Medicare and Medicaid Services not requiring nursing homes to report cases and deaths until May 2020, well into the pandemic. The new estimates rely on numbers from states that required fuller reporting.

Nursing homes and long-term care facilities house a tiny proportion of the U.S. population but they have been estimated to account for about 3 in 10 deaths from COVID-19. Vaccines have brought some relief, dramatically reducing cases and deaths, but concerns remain.

Last month, President Joe Biden announced that his administration would require that nursing home staff be vaccinated against COVID-19 as a condition for those facilities to continue receiving federal Medicare and Medicaid funding.

“If you visit, live or work in a nursing home, you should not be at a high risk for contracting COVID from unvaccinated employees,” Biden said then.

Hundreds of thousands of nursing home workers are not vaccinated, according to federal data, despite those facilities bearing the brunt of the early COVID-19 outbreak and their workers being among the first in the country to be eligible for shots.