According to a new survey released Monday by the American Society for Microbiology and Research America, the percentage of American adults who support vaccination has fallen.

Only 71% of those surveyed said it was “very important” to have their children vaccinated, down from 82% in 2008. The survey also saw a drop in the percentage of those who were confident in the system’s evaluation of the safety of vaccines, down to 77% from 85% 10 years ago.

While actual vaccination levels have not dropped significantly (less than 1% of toddlers have not received any vaccines nationally), the changing mentality for some could be problematic for everyone. According to U.S. News & World Report, public health officials have noted that vaccines work best when they create “herd immunity”—in which a great enough percentage of the population is immune, thereby curbing the spread of a virus. But in order to create herd immunity, 80-95% of the population needs to be vaccinated.

In some cases, the repercussions are already being seen: the incidence of a number of vaccine-preventable diseases has increased in recent years. Whooping cough has jumped from 1,000-10,000 cases a year in 1965 to as many as 48,277 cases in 2012. Measles, too, a virus that was effectively eliminated in 2000, affected over 600 across the country in 2014.

The changing attitudes seen amongst Americans could be attributed at least in part to the growing anti-vaccine movement, a position that has seen the support from numerous public figures, including Donald Trump.

Healthy young child goes to doctor, gets pumped with massive shot of many vaccines, doesn't feel good and changes – AUTISM. Many such cases!

— Donald J. Trump (@realDonaldTrump) March 28, 2014

Nevertheless, there is no reason to worry—yet. Over 90% of kids under the age of 3 have been vaccinated against measles, mumps, rubella, hepatitis B, chickenpox, and polio, while more than 80% have had their vaccines for Haemophilus influenzae, diphtheria, tetanus, pertussis, and pneumococcal infections.