The following article originally appeared in FiercePharma and was written by Beth Snyder Bulik

As coronavirus vaccines edge closer to market, the next question is how pharma companies and public health authorities will convince people to get them.

Civis Analytics decided to test what kind of messages might work. The data firm created five different themed messages and random tested them with 4,000 respondents. They compared the results to the control group in which 73% said they were likely to get a COVID-19 vaccine.

The result? Personal stories proved to be the best motivator for COVID-19 vaccinations. When people saw a mock ad about a real person, in this case a young healthy person who contracted COVID-19 and died, they were 5% more likely than the control group to say yes to a vaccine.

The worst-performing message? Community protection. When people were shown an ad that emphasized the value of herd immunity and role of vaccines in making communities healthier for everyone, they were 1% less likely to get the vaccine. However, even more concerning was that by Civis’ calculations, there was a 69% probability that the community protection message would create a negative backlash.

The three other messages focused on safety, economic recovery and statistics. Statistical laundry lists about COVID-19 as a leading cause of death in the U.S.—and prolonged symptoms and health problems for those who have recovered—were neutral with most groups. The exception was adults ages 50 to 64; the percentage of people in that group likely to vaccinate rose by 6 percentage points in response to those messages/

The economic recovery and safety messages also came with a 57% and 45% chance chance of sparking backlash, respectively.

However, it was the sizeable potential backlash from the community message that most surprised Civis. That’s because in its previous flu vaccine message tests, community protection has always been the top motivator, said Director of Healthcare Analytics Crystal Son. Son previously worked as an infection control epidemiologist at Memorial Sloan-Kettering Cancer Center.

Why the lack of altruism around COVID-19 vaccines versus flu? While Civis didn’t ask that specific question, Son hypothesized that not only has COVID-19 become widely politicized, but vaccines for it have, too. Flu is a more familiar annual routine vaccination that people feel OK about getting to help others.

A key takeaway from the study is that pharma and public health agencies won’t be able to simply replicate vaccination strategies for other viruses or diseases.

Civis plans to periodically repeat the coronavirus message testing because as Son noted, it’s likely that both the baseline and persuasive message sway will change over time.