Drug manufacturers are trying to develop a vaccine for the new coronavirus as quickly as possible in an effort to slow its spread. But scientists and medical experts are concerned that moving too quickly to release a vaccine for the virus could create added risk. Studies suggest that coronavirus vaccines carry the risk of what is known as vaccine enhancement. This is a condition in which the vaccine can make the disease worse when a vaccinated person is infected with the virus. Scientists do not know what causes vaccine enhancement, but it has prevented the successful development of a coronavirus vaccine. There are many coronaviruses, such as the one responsible for Severe Acute Respiratory Syndrome, in 2003, also known as SARS. Other coronaviruses have been linked to Middle East Respiratory Syndrome, known as MERS, and even the common cold.