In the spring of 2009, with H1N1 influenza circulating in the community, Danielle Ofri, a doctor at New York’s Bellevue Hospital, was swamped with panicked patients clamouring for a vaccine. Some called once a week to see if one was available.

But six months later, when the vaccine finally arrived, many of those same patients refused to get it. It wasn’t safe, they told her – “I’m not putting that in my body.” Having exhausted their fears about the actual virus, the vaccine had been replaced as the bigger threat.

Now, working at a hospital battered by COVID-19, Dr. Ofri fears the same pattern: that by the time a vaccine for the novel coronavirus that causes the disease finally arrives – if it does – a segment of the population may turn down, as she puts it, our best chance to save lives and end the pandemic.

Others may require a nudge to take it, which experts suggest makes it important to start early with communicating sound science about vaccines.

“It is important to be pro-active, instead of leaving an empty space for vaccine critics to fill the information void,” said Eve Dubé, a medical anthropologist at Laval University, who recently received a grant from the Canadian Institutes of Health Research to monitor social media for concerns and conspiracy theories being raised about the pandemic, including a possible vaccine.

“Once the trust in vaccination is weakened,” Dr. Dubé said, “we are vulnerable to crisis.”

As the very diseases that vaccines have successfully prevented disappear from public view, anxiety and conspiracy theories around vaccines have only grown. Last year, the World Health Organization identified “vaccine hesitancy” as one of the 10 threats to global health.

The narrative around a COVID-19 vaccine may contribute to safety concerns, given the global race to approve and manufacture possible candidates. In a March survey of nearly 7,000 people, 15 per cent of Canadians and 20 per cent of Americans said they wouldn’t get a COVID-19 vaccine if it were available, said Steven Taylor, a psychologist at The University of British Columbia, and one of the study’s co-leads. In both the United States and Canada, criticism and protests of lockdown measures have included anti-vaccine messaging.

Researchers such as Dr. Dubé and Dr. Taylor argue that rational, science-based messaging about the vaccine needs to begin early, especially at a time when the public is saturated with health information about the pandemic, both accurate and misleading.

A vaccine for COVID-19 is still a year away, even according to optimistic estimates. One sign of progress came this week with an announcement by the American company Moderna that eight subjects participating in an early trial had developed antibodies to COVID-19, and the vaccine was moving ahead to next-stage testing. But each new report of vaccine trials also creates a flurry of headlines and social media traffic – and past incidents show that bad science can suddenly shift public opinion, in some cases irrevocably.

Dr. Dubé cites the example of Ireland and Denmark, which saw vaccination rates for HPV (human papillomavirus) fall to below 50 per cent from about 80 per cent after negative news about the vaccine spread in the media. The most famous modern case of bad vaccine science spreading fear in the public happened in 1998, when a now-debunked paper linked the MMR vaccine (measles, mumps and rubella) to autism. The paper, published in the leading medical journal The Lancet, was retracted years later, but the false findings and their effects persist.

Misinformation about one kind of vaccine can also spread to others. In the case of COVID-19, Dr. Taylor said, any traction on anti-vaccination rhetoric may prove particularly worrisome if a possible second wave of the coronavirus arrives in the middle of influenza season, when getting a flu shot may be especially important.

While most Canadians are vaccine positive and child immunizations have held relatively steady in Canada, Dr. Dubé said that studies estimate that one-third of parents fall into the category of vaccine hesitant, which means they may refuse certain vaccines or delay their children receiving them. A 2016 Canadian study found doctors and nurses reported spending an increasing amount of time answering questions and concerns from parents.

The reasons why people refuse or delay vaccines varies, from suspicions of Big Pharma, to heightened anxiety about safety and a belief in natural immunity, said Dr. Taylor, who wrote last year’s book The Psychology of Pandemics: Preparing for the Next Global Outbreak of Infectious Disease.

Another common reason for avoiding vaccines is a fear of needles – the delivery system for any COVID-19 vaccine. A 2019 meta-analysis of 35 studies published in the Journal of Advanced Nursing concluded that 16 per cent of adult patients, 27 per cent of hospital employees and 18 per cent of staff in long-term care facilities avoided the flu shot because of “needle fear.”

Colliding with the range of concerns about vaccines, Dr. Taylor said that mandatory vaccination tends to only cement resistance because the policy is seen as infringing on personal freedom. The vaccine hesitant group, however, can often be convinced with the right kind of messaging, particularly when the source of their concern is addressed with clear scientific answers.

One complicating factor around COVID-19 has been the message that most healthy people who contract the virus will recover easily and may not even have symptoms. In that case, Dr. Taylor said, many people may respond to a more altruistic message – that they are getting a vaccine not to protect themselves, but to save the lives of vulnerable populations, such as the elderly and those with chronic conditions.

It may be that the deaths and illness caused by COVID-19 have been so devastating, and the economic impact so shattering, that people will line up for the vaccine.

But Dr. Taylor suggested public health officials need to “plan ahead,“ to prevent misinformation from gaining ground. “It would be foolish to wait until the problem arose,” he said – a lesson, he noted, that COVID-19 has already delivered.

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