Vaccination is an incredibly emotional topic for supporters and critics alike. The Mercury’s recent story by Kylie Matthews (To needle or not?) presents viewpoints of both proponents and critics. The article cites Meryl Dorey of the Australian Vaccination Network (AVN), a citizens’ group that advocates parental choice and provides information about the negative aspects of vaccination. The AVN has been operating for 17 years. In 2009, a pro-vaccination group was set up titled Stop the Australian Vaccination Network (SAVN), with the express aim of shutting down the AVN. The methods used by SAVN disturbed me. SAVN essentially rejects free speech critical of vaccination.Before continuing, I need to say I don’t have a strong personal view about vaccination, having no children. My interest in the issue stems from my concern for free speech. I’ve been studying scientific controversies for decades, such as debates over nuclear power, pesticides, fluoridation, climate change and the origin of AIDS. One thing I’ve studied is attacks on dissident experts. On issues such as pesticides and nuclear power, scientists who do research which threatens vested interests are at risk of harassment, denial of research grants, blocking of publications and even dismissal.Dissident scientists are especially vulnerable because their expertise helps change an issue from having only one credible viewpoint to being debatable. Citizen campaigners are usually left alone. Therefore I was shocked by what was happening in the Australian vaccination debate. The AVN was simply providing information from its viewpoint, through a magazine, emails, a website and personal contact. Citizen critics of the dominant view on pesticides, fluoridation, nuclear power and climate change have done this, seldom with any problem.SAVN’s Facebook page, with thousands of members, is filled with contemptuous comment about the AVN and especially about its key figure Meryl Dorey. SAVN members made dozens of complaints about the AVN to government agencies including the Health Care Complaints Commission, the Department of Fair Trading, and the Office of Liquor, Gaming and Racing. These complaints diverted the AVN from its normal activities.Other opponents of the AVN posted on the web the names, addresses and phone numbers of advertisers in the AVN’s magazine Living Wisdom, opening them to potential harassment. Some AVN members received pornographic images.I received a taste of harassment myself. After I wrote articles defending free speech by critics of vaccination, one SAVN member wrote to me calling my work “unethical” and “dishonest”. Others made comments on SAVN’s Facebook page, for example calling me an “idiot” and a “moron”. One SAVN member made a complaint about my work to the University of Wollongong (UOW) Vice-Chancellor. Fortunately the university administration has defended my freedom to research the vaccination controversy. One of the best ways to respond is to expose these methods, and to do so in a calm, informative manner.I wrote a careful response to the comments by SAVN members, documenting their methods, and posted it on my website. This seems to have worked a charm: no SAVN member has challenged my account. - Brian Martin is professor of social sciences at UOW.