WASHINGTON - US leading reference books publisher Merriam-Webster announced Monday that "vaccine" has been chosen as the company's 2021 word of the year, following a year in which mass vaccination against COVID-19 has been carried out in the country and debate over the shots has never abated.

The company said there are primarily two reasons for the selection: the role vaccines played in stopping the spread of the virus, and the nationwide discussion over how to deal with inoculations that was oftentimes laced with people's political views.

"The word vaccine was about much more than medicine in 2021. For many, the word symbolized a possible return to the lives we led before the pandemic. But it was also at the center of debates about personal choice, political affiliation, professional regulations, school safety, healthcare inequality, and so much more," Merriam-Webster wrote in a statement.

The company said lookups of the word vaccine skyrocketed by 601 percent from 2020, while interest in the word has increased since the onset of the pandemic, before the vaccines were rolled out. Lookups of the word grew by 1,048 percent in 2021 from 2019, according to the company.

"The promising medical solution to the pandemic that upended our lives in 2020 also became a political argument and source of division. The biggest science story of our time quickly became the biggest debate in our country, and the word at the center of both stories is vaccine," read the statement.

The company noted that throughout 2020, the discussion was focused predominantly on funding, development, testing, and ultimate distribution of the vaccines, whereas since August, "discussions about policy, approval, and vaccination rates-rather than the vaccine itself-sent people to the dictionary."

Merriam-Webster also named 10 runner-up words of the year, namely insurrection, perseverance, woke, nomad, infrastructure, cicada, Murraya, cisgender, guardian and meta.