Ever since the release of Gardasil, Merck’s famed HPV vaccine, doctors and medical organizations have sung its praises and pushed parents to get their preteen daughters vaccinated. But while many states are weighing whether to make the shot mandatory, authors of a new article in the New England Journal of Medicine say caution is still needed because:

  • Gardasil’s long-term effectiveness is unclear;
  • It is expensive;
  • It only protects against some of the viruses that cause cervical cancer, so women still need regular pap screenings;
  • And it is linked to thousands of side effects–some more serious than others.

Dr. Carolyn J. Haug, editor of the Journal of Norwegian Medical Association, wrote in the New England Journal editorial that the long-term impact of the HPV vaccination will not be observable for decades. Thus, ”with so many essential questions still unanswered, there is good reason to be cautious.”