We do not know the who, how or why of the "mounting pressure" but here is a list of the sponsors of the 2015 Tribeca Film Festival https://tribecafilm.com/sponsor-block. Was the pressure from these commercial entities or from other places? Wherever it came from, open dialogue about vaccination has suffered a major defeat.
Official CDC data and the Vaccine Adverse Event Reporting System (VAERS) show that nobody has died from measles in the US in over 10 years, whereas there have been at least 108 deaths reported to VAERS during the same period linked to measles vaccines. It is generally acknowledged by public health experts that VAERS reports represent between 1-10% of all cases so we are talking about anywhere from 1080 to 10800 measles vaccine deaths in the US per year against 0 measles deaths!