As an epidemiologist, I wholeheartedly agree with James Poniewozik that putting Jenny McCarthy in a position to promote her anti-vaccine stance poses a danger to the nation’s public health. (“Bad Medicine,” July 29, 2013) However, it is also equally dangerous for Mr. Poniewozik to describe our current knowledge of vaccine safety as “medical fact.” When it comes to vaccines and medicines, there are few hard facts, which is why we only make strong statements after many, many studies have tested a hypothesis. And even then, knowledge may change after the 50th study is performed. If vaccine safety was medical fact, then the CDC would not spend hundred of millions annually on vaccine surveillance. It is our ongoing collection of data that gives us some peace of mind, not the ability to draw a line in the sand and say “now we know.”
Dan Ollendorf, Lexington, Massachusetts