Health organisations say their doctors and nurses are facing unprecedented levels of online abuse for speaking out on coronavirus.
Anti-vaxxers and Covid-deniers have consistently targeted medics who have encouraged people to protect themselves with the jab.
A letter signed by groups including the Academy of Medical Royal Colleges, the NHS Confederation, the British Medical Association and the Royal College of Nursing calls for an end to the torrents of trolling.
It was prompted by the barrage of abuse directed at Gill Walton, chief executive of the Royal College of Midwives, after she urged pregnant women to get vaccinated.
Some of the tweets compared her and other nurses to serial killer Myra Hindley and the Nazis.
Ms Walton said: "Over the past 16 months, health and care workers have been working under incredible stress, with increased demands and less staff because of the pandemic, yet still they have strived to provide the best possible care.
"I know the vast majority of the public are incredibly grateful for that dedication and commitment.
"However, too many health and care workers have faced abuse from a small but vocal minority, from COVID deniers to anti-vaxxers.
"Our midwives, doctors, nurses, porters, cleaners, everyone working for the NHS, has the right to safety and respect in the workplace.
"To those who abuse us for simply making polite requests to wear masks or to maintain social distance in hospitals or GP practices, to those who deny the existence of the pandemic or the science of vaccination, to those who issue death threats or incite violence against us, we say enough is enough."
Other health workers have been abused after trying to boost vaccination uptake among young adults.
Dr Samantha Batt-Rawdon, president of the Doctors' Association UK, said she had blocked dozens of abusive accounts since the pandemic started.
"Twitter should be a safe space for doctors to speak up about the importance of vaccination but all we have got back is a wall of abuse,” she said. “Frankly this is the last thing any of us need right now."
Professor Helen Stokes-Lampard, chair of the Academy of Medical Royal Colleges, said: "We now need to be more united than ever and show our solidarity by calling out the aggressive and unreasonable behaviour of a small minority."