Jacob King – Pool / Getty Images

As the U.S. and other countries prepare to roll out millions of messenger Ribonucleic Acid (mRNA) vaccinations, UK officials warn the still experimental mRNA vaccinations will do nothing to stop the spread of the virus.

The U.S., Canada and the UK recently approved the vaccine developed by Pfizer and the German firm BioNTech for “emergency use.”

But critics of the rollout say the mRNA vaccinations were not designed to stop the spread of a virus since, unlike traditional vaccines, the mRNA vaccines are bio-engineered to genetically modify human DNA.

In a letter sent Nov. 4 to the U.K.’s healthcare staff in four countries, chief medical officers say the vaccines will not stop the spread of the virus, and healthcare workers should prepare for “an specially hard winter.”

“[Vaccine] deployment will have only a marginal impact in reducing numbers coming into the health service with COVID over the next three months,” the officials wrote.

“Vaccines do not equal zero COVID,” World Health Organization emergencies director Michael Ryan warned on Friday.

The vaccines pose a problem to healthcare workers because of the serious side effects reported by participants in clinical trials.

Buddy Creech, one of the lead investigators of the Moderna vaccine trials, said the side effects are strong enough to put health workers “out of commission” and those risks have to be raised before the vaccines are rolled out.

Officials at Massachusetts General Hospital and other hospitals in the U.S. are considering vaccinating doctors and nurses at the end of their shifts to stagger their staff in case they call out sick after receiving the shots.

But Mass General’s vice chair of emergency preparedness Paul Biddinger says staggering shifts will not be enough since full data from Pfizer and Moderna’s late-stage trials are still unknown.