EMBED >More News Videos Danielle Leigh looks into questions regarding the legality of mandating vaccines.

WILLIAMSBURG, Brooklyn (WABC) -- New York City Mayor Bill de Blasio declared a public health emergency Tuesday in the ongoing measles outbreak affecting the Orthodox Jewish community and ordered mandatory vaccinations in several neighborhoods.The order applies to anyone living, working or going to school in four zip codes in Williamsburg and requires all non-vaccinated people who may have been exposed receive the measles-mumps-rubella (MMR) vaccine, including all children over 6 months old.Those zip codes are 11205, 11206, 11211 and 11249.Under the mandatory vaccinations, members of the city's Department of Health and Mental Hygiene will check the vaccination records of any person who may have been in contact with infected patients. The city can't legally physically force someone to get a vaccination, but those who have not received the MMR vaccine or do not have evidence of immunity may be given a violation and could be fined $1,000."There's no question that vaccines are safe, effective and life-saving," de Blasio said. "I urge everyone, especially those in affected areas, to get their MMR vaccines to protect their children, families and communities."The order raises questions about the legality of mandating vaccines, and New York Civil Liberties Union Executive Director Donna Lieberman issued the following statement:7 On Your Side Investigates' Danielle Leigh also looked into the questions of legality:The public health emergency declaration comes one day after the city threatened to close yeshivas if non-vaccinated students are allowed to attend classes during the current measles outbreak.There have been 285 cases since the outbreak began last October, though it is unclear how many cases are current. There have been no fatalities and only three measles-related deaths in the past two decades, but health officials say there have been complications in the current outbreak, including 21 hospitalizations.In December, the health department ordered yeshivas and childcare centers serving the Orthodox Jewish community in the affected zip codes in Brooklyn to exclude all non-vaccinated students from attending school or daycare until the outbreak was declared over. But in January, one yeshiva in Williamsburg fell out of compliance with the exclusion mandate, allowing non-vaccinated children back into school or daycare.Officials say this single yeshiva is connected to more than 40 cases.The health department has since issued Commissioner's Orders to all yeshivas in Williamsburg to comply with the mandatory exclusion of non-vaccinated children or face violations subject to fines and possible school closure.The city's health commissioner, Dr. Oxiris Barbot, said that the majority of religious leaders in Brooklyn's large Orthodox communities support vaccination efforts, but that rates have remained low in some areas because of resistance from some groups that believe the inoculations are dangerous."This outbreak is being fueled by a small group of anti-vaxxers in these neighborhoods," she said. "They have been spreading dangerous misinformation based on fake science. We stand with the majority of people in this community who have worked hard to protect their children and those at risk. We've seen a large increase in the number of people vaccinated in these neighborhoods, but as Passover approaches, we need to do all we can to ensure more people get the vaccine."Measles is a highly contagious disease and can cause pneumonia, encephalitis, and in rare cases, death. The vast majority of cases are children under 18 years of age, while there have been 39 cases in adults.Health officials say individuals traveling to areas with ongoing large outbreaks, including Israel, Europe, upstate New York, and other parts of the United States should make sure they and their children are appropriately vaccinated with MMR.For more information on the MMR vaccine, call 311 or CLICK HERE ----------