Medical workers transport a patient from an ambulance to George Washington University Hospital in Washington D.C., the United States, May 13, 2020. (Photo by Ting Shen/Xinhua)

Official tallies of deaths due to COVID-19 in the United States underestimated the full increase in deaths associated with the pandemic in many states, according to a new study published on Wednesday.

The study, published in the journal JAMA Internal Medicine, found that the number of deaths due to any cause increased by approximately 122,000 from March 1 to May 30, which was 28 percent higher than the reported number of COVID-19 deaths.

To estimate the burden of all deaths related to COVID-19 in the United States from March to May, researchers evaluated the numbers of U.S. deaths from any cause and deaths from pneumonia, influenza, and COVID-19.

Evaluating unexplained increases in deaths due to all causes or attributed to nonspecific outcomes, such as pneumonia and influenza, can provide a more complete picture of the burden of COVID-19, according to the study.

The number of excess all-cause deaths was 28 percent higher than the official tallies of COVID-19-reported deaths during that period, the study found.

Excess deaths provided an estimate of the full COVID-19 burden and indicated that official tallies likely undercounted deaths due to the virus. The mortality burden and the completeness of the tallies varied markedly between states, according to the study.