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Does Moderna have a booster vaccine?

The pharmaceutical company is in the market for developing a third vaccine dose as the US heads towards a nervous winter.

Moderna vials sit on a table before they are loaded into syringes at a mobile Covid-19 vaccination clinic in Bridgeport, Connecticut.
Joseph PreziosoAFP

How effective is the Moderna jab?

After two doses the Moderna jab is 93% effective in "real-world" conditions. Moderna also said that this efficacy lasts for six months after the second dose, prompting their trials on the usefulness of a third vaccine. Six months would coincide with the winter season for most people in the United States.

This doesn't mean it's impossible for the vaccinated to catch covid-19, but it is extremely unlikely for the fully-vaccinated to develop serious symptoms. The CDC recommends the double-vaccinated to continue wearing masks to stop the spread of symptomless covid-19.

Why is the company recommending a third dose?

Despite just over 50% of the US population vaccinated, there has been a worrying rise in cases driven by the Delta variant of covid-19. The new variant is much more infectious than previous variants. It has forced some states to reimpose some restrictions and others to impose vaccine mandates on federal workers. As the country heads towards winter, where more of the population will be indoors, there will be a higher risk of infection in comparison to the summer.

For recently vaccinated individuals the Delta variant poses little threat. However, for those whose vaccines were administered at the beginning of the year there could be a risk by the fall that they have lost some of their effectiveness. This could in turn lead to what are called 'breakthrough cases,' where people are reinfected with covid-19 but at a stage that could put their health seriously at risk. While vaccine efficacy remains high there is no problem; 97% of all covid-19 hospital cases in the US are for those who have been unvaccinated.

What is the science behind a third dose?

Moderna posted new information as part of its second-quarter earnings release where it claimed a third dose may be needed as the Northern Hemisphere heads into winter. The company said both a third shot of the original vaccine and new versions have demonstrated “robust antibody responses to COVID-19 variants of concern.” Tests for a third jab reportedly give the same level of protection as someone who received the original two does for the first time. The information has been submitted to a peer-reviewed journal.

A United Kingdom trial will test different combinations of boosters, using a different vaccine from the original inoculations. Preliminary studies of these ‘mix and match’ strategies suggest that they could lead to more robust immune responses. “It appears that the Pfizer vaccine boosted antibody responses remarkably in one-dose AstraZeneca vaccinees. This is all around wonderful news,” says Zhou Xing, an immunologist at McMaster University in Hamilton, Canada.


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