In short
mRNA-1647 is an investigational vaccine being studied to prevent cytomegalovirus (CMV) infection. It is a messenger RNA (mRNA) vaccine, a type of vaccine that uses genetic instructions to teach the body to recognise and fight a virus. The vaccine has been tested in a completed Phase 3 trial involving 7,484 healthy participants aged 16 to 40 years.
Key points
- mRNA-1647 is an investigational vaccine against cytomegalovirus (CMV).
- The vaccine was studied in a Phase 3 trial that has been completed.
- The trial enrolled 7,484 healthy participants aged 16 to 40 years.
- The main goal was to see if the vaccine could prevent primary CMV infection in CMV-seronegative female participants.
- The vaccine was given as three intramuscular injections of 100 micrograms.
- The trial also measured safety and reactogenicity after each injection.
What is mRNA-1647?
mRNA-1647 is an investigational vaccine against cytomegalovirus (CMV), a common virus that can cause serious health problems in babies infected before birth and in people with weakened immune systems. The full name of the active substance is MRNA encoding human cytomegalovirus glycoprotein L. It is a messenger RNA (mRNA) vaccine, meaning it contains genetic instructions that tell cells in the body to make a piece of the virus, which then helps the immune system learn to recognise and fight the real virus. mRNA-1647 is not an authorised medicine; it is still being studied in clinical trials.
How does mRNA-1647 work?
mRNA-1647 works by delivering messenger RNA into the body's cells. This mRNA carries the code for making a protein from the outer surface of cytomegalovirus, called glycoprotein L. Once the cells make this protein, the immune system sees it as foreign and produces antibodies and immune cells against it. If the vaccinated person later comes into contact with the real CMV virus, the immune system is already prepared to recognise and attack it, which may prevent infection. The trial data do not provide further details on the exact immune response measured.
Which conditions is mRNA-1647 studied for?
- Cytomegalovirus infection (CMV) — a viral infection that is usually mild in healthy people but can cause serious illness in unborn babies and in people with weakened immune systems.
How is mRNA-1647 given?
In the Phase 3 trial, mRNA-1647 was given as an intramuscular injection at a dose of 100 micrograms. The vaccine was administered on a three-dose injection schedule. The comparison arm in the trial received sodium chloride 0.9% solution for injection, also given intramuscularly, which served as a placebo.
What do the clinical trials show?
One completed Phase 3 trial has evaluated mRNA-1647 in healthy participants aged 16 to 40 years. The trial enrolled 7,484 participants and investigated whether the vaccine could prevent primary CMV infection, defined as seroconversion from a negative to a positive result for serum IgG against one of four CMV antigens not encoded by the vaccine (pp150, pp28, pp52, pp38), assessed starting 28 days after the third injection. The trial's main efficacy goal was to demonstrate prevention of primary CMV infection in CMV-seronegative female participants. Safety and reactogenicity were also evaluated, including solicited adverse reactions through 7 days after each injection, unsolicited adverse events through 28 days after each injection, medically attended adverse events from Day 1 through 6 months after the last injection, adverse events of special interest from Day 1 through end of study, and serious adverse events from the time of consent through end of study. The trial status is completed, meaning the study has finished and results are being or have been analysed.
What side effects are known?
The sources provided for this page do not include information on side effects of mRNA-1647. The Phase 3 trial measured safety outcomes, including solicited and unsolicited adverse reactions, but the results are not reported in the data available here.