A new study conducted to evaluate mRNA-1273, a Covid-19 vaccine candidate, manufactured by Moderna, Inc, provides evidence that the vaccine can prevent symptomatic infection.

The preliminary findings of the study, published in The New England Journal of Medicine , stated the vaccine has demonstrated 94.1 per cent efficacy in preventing symptomatic Covid-19.

For the study, the researchers studied over 30,000 participants randomized to receive the vaccine or a placebo. 11 of those in the vaccine group developed symptomatic Covid-19 compared to 185 participants who received the placebo.

Cases of severe Covid-19 occurred only in participants who had received the placebo.

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Lead author, Lindsey Baden, MD, an infectious diseases specialist in the Brigham, said in a statement: “Our work continues. Over the next months, we'll have increasing amounts of data to better define how this vaccine works, but the results so far show a 94.1 percent efficacy. These numbers are compelling.”

"And, importantly, the data suggest protection from severe illness, indicating that the vaccine could have an impact on preventing hospitalizations and deaths, at least in the first several months post-vaccination,” Baden added.

Overall, reactions to the vaccine were mild — about half of the recipients experienced fatigue, muscle aches, joint pain, and headaches, more so after the second dose, the study said.

The researchers noted that in most cases, such effects started about 15 hours after the vaccine and resolved after two days without sequel . While a similar number of adverse events were reported in the placebo and vaccine groups.

“While these results are encouraging, they are limited by the short duration of follow-up so far. Longer-term data from the ongoing study may allow us to more carefully evaluate the vaccine's efficacy among different groups, determine the impact on asymptomatic infection, understand when immunity wanes, and determine whether vaccines affect infectiousness,” said Baden.

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