Russia's meddling online went beyond the 2016 US presidential election and into public health, amplifying online debates about vaccines, according to a new study.

The recent research project was intended to study how social media and survey data can be used to better understand people's decision-making process around vaccines. It ended up unmasking some unexpected key players in the vaccination debate: Russian trolls.

The study, published in the American Journal of Public Health on Thursday, suggests that what appeared to be Twitter accounts run by automated bots and Russian trolls masqueraded as legitimate users engaging in online vaccine debates. The bots and trolls disseminated both pro- and anti-vaccine messages between 2014 and 2017.

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When it came to the Russian troll accounts, the researchers found 253 tweets containing the #VaccinateUS hashtag among their sample. Among those tweets with the hashtag, 43% were pro-vaccine, 38% were anti-vaccine, and the remaining 19% were neutral.

By posting a variety of anti-, pro- and neutral tweets and directly confronting vaccine skeptics, trolls and bots "legitimize" the vaccine debate, the researchers wrote in the study.

"This is consistent with a strategy of promoting discord across a range of controversial topics -- a known tactic employed by Russian troll accounts. Such strategies may undermine the public health: normalizing these debates may lead the public to question long-standing scientific consensus regarding vaccine efficacy," they wrote.