New Delhi, April 28 : There has been a 27 per cent spike in anti-vaccine posts on X.com (formerly Twitter) after Covid-19 shots were introduced, according to a new study.

Using open-source software (the Snscrape library in Python), researchers from Stanford University in the US downloaded 567,915 posts with the hashtag "vaccine" from January 1, 2018 to December 31, 2022.

The analysis via machine learning algorithm showed that 458,045 were negative and 109,870 were positive. Posts that were negative in sentiment were predominant both before and after vaccines became available.

However, after Covid vaccines were introduced in December 2020, there was a marked increase in the number of posts about vaccines, with 10,201 more vaccine-related tweets per month, on average, than would be expected if vaccination hadn't started.

"There was also a marked increase in negativity. There were 310,508 posts (approx. 12,420 a month on average) with negative sentiment after December 11, 2020. This is 27 per cent more than the 244,635 (9,785 a month) that would be expected if Covid vaccination hadn't started," revealed the study, presented at the ongoing ESCMID Global Congress in Barcelona.

"Social media has the power to exponentially amplify health messages, both beneficial and harmful, and is an arena in which political figures, actors, singers, personalities and other 'influencers' outnumber healthcare voices," said lead researcher Dr Guillermo Rodriguez-Nava, of Stanford University School of Medicine.

"Unfortunately, in some countries, negative sentiments toward vaccines are not only health-related but also religious and political. This is a complex issue, with no easy solution, but we do need to change our approach because it is clearly not working," Rodriguez-Nava said.

The researcher proposed "avoiding derogatory terms such as 'anti-vaxxers', and perhaps even 'misinformation,' and approaching these individuals in a more respectful and understanding manner".

/IANS