Following the availability of COVID-19 vaccines, there was a noticeable surge in negativity surrounding vaccines on Twitter. Researchers at the ESCMID Global Congress (formerly ECCMID) in Barcelona, Spain (held from 27th to 30th April) made this observation. The analysis revealed that spikes in negative tweets coincided with announcements from governments and healthcare authorities regarding vaccination. To address this issue, the researchers propose adopting a fresh approach to discussing vaccines—one that avoids using the term "anti-vaxxers." Dr. Guillermo Rodriguez-Nava, lead researcher from Stanford University School of Medicine, Stanford, USA, emphasized the significance of vaccines as one of humanity's greatest achievements. Vaccines have the potential to eradicate dangerous diseases like smallpox, prevent deaths from illnesses with 100% mortality rates (such as rabies), and even protect against cancers caused by HPV. Despite these benefits, opposition to vaccine use has grown in recent years. Negative voices have already had consequences, with measles re-emerging in countries where it was once considered eradicated. This situation not only affects children who cannot decide for themselves but also impacts immunocompromised patients who cannot receive vaccinations. Dr Rodriguez-Nava and colleagues analyzed COVID-19 vaccine-related posts on Twitter. They used open-source software (the Snscrape library in Python) to download tweets with the hashtag "vaccine" from 1 January 2018 to 31 December 2022. Cutting-edge AI methods were then employed for sentiment analysis, classifying tweets as either positive or negative. Additionally, they created a "counterfactual scenario" to understand how tweet patterns would have looked if COVID-19 vaccines hadn't been introduced in December 2020. The results showed that both before and after vaccine availability, negative sentiment tweets dominated. For instance, one negative tweet read: "The EU Commission should immediately terminate contracts for new doses of fake #vaccines against #COVID19 and demand the return of the €2.5bn paid so far. Everyone who lied that #vaccines prevent the spread of the virus must be held accountable." In contrast, positive tweets celebrated vaccination milestones. For example: "Two-month shots! #vaccines are always a reason to celebrate in our house. #VaccinesWork." Since the introduction of COVID-19 vaccines, the number of vaccine-related tweets has increased significantly—10,201 more per month on average than expected if vaccination hadn't started. Negativity also rose, with approximately 12,420 negative sentiment tweets per month after 11 December 2020—27% more than expected without vaccination. The proportion of positive tweets decreased slightly (from 20.3% to 18.8%), while negative tweets increased (from 79.6% to 81.1%) after COVID vaccine introduction. Notably, negative activity spiked during vaccination announcements. For instance, April 2021 saw the highest number of negative tweets—the same month the White House announced COVID-19 vaccine eligibility for all people aged 16 and older. Interestingly, the lowest number of negative tweets occurred in April 2022, the month Elon Musk acquired Twitter. While the exact reason is unknown, it may be related to seasonal patterns (higher negativity during winter) or users focusing on platform changes under new ownership. In summary, negative sentiments about vaccines were already prevalent on social media before COVID-19 vaccines arrived. Their introduction significantly amplified negative sentiments on X (formerly Twitter) regarding vaccines.
