Dozens of drugmakers are racing to develop coronavirus vaccines. Here's how they see 2020 playing out and when the first vaccines might be available.

There are more than 140 coronavirus vaccine projects in the works, according to the World Health Organization.

Research has progressed quickly into human testing, with 16 leading vaccine candidates now being tried on humans in clinical trials around the world.

A Business Insider review found this is just the tip of the iceberg: at least 16 additional vaccines are expected to enter the clinic in 2020. Dozens of additional programs have yet to disclose development timelines. 

Vaccine development is historically a challenging multiyear process, aimed at ensuring a candidate is safe and effective before giving it to millions of healthy people.

There's an urgent need for a vaccine, as coronavirus infections and hospitalizations have started to accelerate in many US states, particularly in the South and West. As of June 26, the US had recorded than 2.5 million infections and over 125,000 deaths attributed to the virus. 

While early research is moving with unprecedented speed, the three biggest challenges lie ahead. Those are generating human data that show a vaccine works, ramping up production to produce gigantic quantities, and distributing a vaccine across the world.

The US government is aiming to have hundreds of millions doses ready of a safe and effective vaccine by January 2021. While US health officials have said that goal is possible, it would be a timeline without precedent in the history of vaccines. Some vaccinologists and industry analysts are "deeply skeptical" that successful research will move that quickly.

Here's a chronology of what to expect in the coming months for potential coronavirus vaccines, from companies and organizations that have put forward development timelines.

Where we are now: 16 programs in human testing with results starting to roll in

Throughout the spring, 16 vaccine programs started human testing. The vast majority of these are still recruiting and innoculating volunteers across the globe, including in the US, the UK, China, Russia and Germany.

The 100-some remaining vaccine projects remain in laboratory testing. Meanwhile, the speediest programs have already started producing initial human data and moving into larger trials.

Moderna's vaccine was the first to produce early human results after starting its first trial on March 16. People given the Massachusetts biotech's vaccine registered levels of antibodies that may suggest protection against the virus, but more testing will be needed. Moderna started in June a second human trial, randomizing 600 people to receive either the vaccine or a placebo.

Moderna isn't alone in testing a vaccine based on messenger RNA (mRNA), a promising yet unproven technology that relies on the genetic code of the virus rather than samples of the particle. While there are no approved mRNA vaccines on market, four of the vaccines in human testing are based on mRNA.

The pharma giant Pfizer and German biotech BioNTech are testing an mRNA vaccine in early human studies in Germany and the US. Another German biotech called CureVac got the OK on June 18 to start testing its mRNA vaccine in Germany and Belgium  And researchers at Imperial College London have also entered the clinic in the UK with a vaccine based on the same platform.

Inovio Pharmaceuticals, a small Pennsylvania company, is testing a DNA-based vaccine, entering the clinic on April 6. The Maryland biotech Novavax started dosing healthy volunteers in Australia on May 25.

China leads the world with six vaccine candidates now being tested in humans. CanSino Biologics has the most advanced effort, entering mid-stage clinical trials in April. The first human data was released on May 22 in The Lancet, a top medical journal.

While the results support additional trials, they also showed most participants registering some level of side effects, with about 8% suffering from a severe fever. CanSino's Phase 2 trial is not testing the strongest dose used in the small safety study, likely because of the increased rate of side effects.

The other Chinese vaccines were developed by the biotech Clover Biopharmaceuticals, the state-owned pharma Sinopharm, the private biotech Sinovac, the Chinese Academy of Medical Sciences, and Chongqing Zhifei Biological Products.

The South Korean biotech Genexine has started enrolling patients into its first clinical trial for a coronavirus vaccine called GX-19, anticipating preliminary data in September.

In Europe, the British pharma AstraZeneca is leading a vaccine program first developed by University of Oxford researchers. That is expected to soon produce initial results that will guide further testing.

Finally, Russian researchers have started testing in a small group of people a vaccine candidate created by the Moscow-based Gamaleya research institute.

Read more: The US is sprinting to develop a coronavirus vaccine or treatment. Here's how 19 top drugmakers are racing to tackle the pandemic.

Summer 2020: More results roll in, presenting a critical test for early efforts

This summer will be marked by a flurry of early human results from these vaccine programs. None of these trials are designed to definitively test if a vaccine works or not, as these small studies are more focused on making sure it is safe enough to use before testing a vaccine in large groups of people.

Moderna anticipates providing additional data with longer follow-up in more people, about 100, throughout the summer. Its second trial in 600 people should also provide early safety data by July. Barring any red flags, Moderna aims to start a late-stage efficacy trial in July that will enroll 30,000 people — the first drugmaker to reach that stage in development.

A similar dynamic will be in play for most of the 14 vaccine developers now in early human testing: early positive results will support larger, efficacy-focused studies that launch this summer. Drugmakers large and small have outlined this plan, including giants like Pfizer and AstraZeneca along with tiny biotechs like Inovio and Novavax. 

In August, AstraZeneca's vaccine will start its own efficacy trial, likely enrolling 30,000 people as well. Pfizer is planning to start a similarly rigorous study in July or August.

While the fastest vaccine programs will be starting pivotal studies, more candidates will be entering the clinic this summer. 

Most notably, Johnson & Johnson — the world's largest healthcare company — aims to start testing a vaccine candidate in July by enrolling 1,045 healthy volunteers in the US and Belgium.

A handful of tiny biotechs that lack the resources and experience of giants like J&J also hope to begin human testing. Without serious support from governments or industry giants, they face uncertainty on how they can scale up manufacturing, given a lack of resources and experience in mass-producing vaccines.

Stabilitech Biopharma plans to start human testing of an experimental vaccine pill in June. But the small British biotech is also openly soliciting fundraising to support that research. 

In Australia, University of Queensland researchers have outlined plans to start human testing as soon as July.

A trio of three tiny European biotechs — Reithera, Leukocare, and Univercells — have banded together on a vaccine program with the goal of starting this summer a human safety trial in Italy.

The San Francisco biotech VaxArt is preparing a potential oral vaccine taken as a tablet instead of a traditional injection, which could start a safety trial this summer.

Dr. Patrick Soon-Shiong's biotechs ImmunityBio and NantKwest also have an adenovirus-based vaccine that should start human testing this year, likely by the summer and potentially as early as June.

The Canadian company Medicago is aiming to start human trials this summer after its vaccine showed it could produce antibodies in mice after one dose. 

Singapore's government is working with Arcturus Therapeutics, a small San Diego biotech, on an mRNA vaccine expected to start human trials this summer in Singapore.

By the time summer winds down and fall arrives, there should be well over 20 vaccine candidates in human testing. 

Fall and Winter 2020: The fastest vaccines eye emergency use

The three leading vaccine programs — led by Moderna, AstraZeneca, and Pfizer — are aiming for potential emergency use authorization this fall. This regulatory OK would likely make the vaccine available to limited populations at high risk of infection or severe disease, such as healthcare workers and the elderly. 

The US FDA has never allowed emergency use of a vaccine before, and it is unclear what a vaccine program would need to demonstrate to make that happen.

Some of the world's other largest drugmakers are hoping to bring their vaccines into the clinic later this year, forming a second round of vaccine development.

This includes a collaboration between two of the world's largest vaccine businesses, Sanofi and GlaxoSmithKline. This duo is aiming to bring a protein-based vaccine from Sanofi combined with GSK's adjuvant, which could boost an immune response, into human testing in the second half of 2020. They forecast it could be widely available in the second half of 2021. 

Sanofi has an additional collaboration with a tiny Massachusetts biotech for an mRNA vaccine aiming to start human trials in the fourth quarter of 2020. 

Merck, another giant in the vaccines business, unveiled two vaccine candidates on May 26 it plans to bring into the clinic before year's end.

Finally, a few small biotechs are aiming to start human testing in the second half of 2020: the Gaithersburg, Maryland-based AltImmune, Italy's Takis Biotech, Europe's ExpreS2ion Biotechnologies, and the French biotech Valneva.

2021 and beyond

By the time 2021 starts there will likely be 30 or more vaccines being tested in humans.

We still won't fully know how well they work or how safe they are in humans. Regulators will face difficult decisions in the face of a pandemic on how much data is enough to allow them to be used beyond clinical trials.

J&J says its vaccine could be available for emergency use in early 2021. University of Queensland researchers have also stated their vaccine could be used in healthcare workers or vulnerable populations in early 2021. 

Sanofi and GSK's vaccine is aiming to be available in the second half of 2021. 

This story has been updated to reflect an accelerated development timeline for Johnson & Johnson's vaccine candidate.