The Moderna coronavirus vaccine, one of the two approved in the United States for emergency use, should provide immunity against COVID-19 for at least one year, the biotechnology company said in a call with investors.

More tests will follow to see if adding a third dose could extend the protection of the vaccine even further, but this seems to be good news, indicating a level of durable immunity. Ultimately, we could end up doing yearly COVID-19 shots.

Moderna’s chief medical officer Tal Zaks told the JP Morgan 39th Annual Healthcare Conference that the company’s expectation is that “the vaccination should last you at least a year.” He added “there’s an opportunity to boost people” with a third dose, especially the ones at high risk, but for that more tests need to be carried out.

The company had already anticipated that the immunity induced by its vaccine would be protective against the coronavirus variants recently reported in the UK. They had tested previous variants and found the vaccine was equally effective. Now, this new announcement (which isn’t backed up by hard evidence yet) seems to bring another reason for cautious optimism.

Moderna and Pfizer/BioNTech’s vaccines have been granted emergency use authorization from the US Food and Drug Administration. They both require two doses and use messenger RNA (mRNA) technology. This is a different approach from traditional vaccines, which use a weakened or dead version of a virus or a lab-created protein; mRNA vaccines have been in development for a long time, but these are the first two working vaccines using this technology.

Essentially, the two vaccines use a synthesized scrap of genetic information that is packaged in a protective fat layer to keep it from disintegrating. When it enters into the cells, it has molecular instructions to tell the cells to create a protein that triggers an immune response to the spike protein on the surface of the coronavirus. It has absolutely no effect on the human DNA (that would be impossible) — just a blueprint to help the body protect itself against the virus.

After Pfizer and BioNTech reported their coronavirus vaccine had a 90% efficacy, Moderna also announced that its vaccine also prevents the dreaded illness. The company said interim analysis of its Phase 3 showed the experimental vaccine is 94.5% effective at preventing COVID-19, beating even the most optimistic estimates.

Moderna expects to deliver between 600 million and one billion doses of its vaccine in 2021, forecasting vaccine-related sales of $11.7 billion for the year. The company has signed advance purchase agreements with several countries such as Japan, Canada, Israel, and the United States, which agreed to buy 200 million doses.

While the one-year immunity from Moderna is good news, there’s still a long road ahead with the pandemic. The World Health Organization (WHO) said this week that herd immunity to the coronavirus – when enough people have immunity to prevent the disease from spreading – likely won’t be achieved in 2021. Even as vaccines are rolling out, we’re seeing a record-breaking number of cases in many parts of the world.

In addition, the potential for virus mutations, limited access to vaccines in developing countries, and skepticism about vaccination are all mitigating factors to herd immunity. Several countries such as the US and the UK have already started the first states of mass-vaccination campaigns but this won’t be enough for herd immunity this year.

“We are not going to achieve any levels of population immunity or herd immunity in 2021,” WHO chief scientist Dr Soumya Swaminathan told a media briefing. She highlighted the “incredible progress” made by researchers to develop vaccines and asked people to be “a little patient” as rolling out the vaccines “takes time.”

More than 91 million people have so far tested positive for coronavirus worldwide, with 1.9 million deaths, according to data compiled by Johns Hopkins University. Meanwhile, the vaccine campaign is moving along around the world, with more than 29 million shots already given in 38 countries, data by Bloomberg showed.