When will a COVID-19 vaccine be available? How effective will it be? Those are two of the most pressing questions being asked by many with the number of COVID-19 cases rising in much of the U.S. 

Unfortunately, the questions can't be answered yet with a high level of confidence. But there are 23 COVID-19 vaccine candidates currently in clinical testing, according to the World Health Organization (WHO). The progress of these candidates can at least provide a clue as to when a COVID-19 vaccine might be available. Here are those vaccine candidates and how likely they could be to win regulatory approval.

Coronavirus vaccine bottles

Image source: Getty Images.

In phase 1 testing

The field of early stage COVID-19 vaccine candidates is crowded. Of the 23 COVID-19 vaccine candidates currently in clinical testing, 18 are in phase 1 studies:

Organization(s)

Vaccine Candidate

Status 

AnGes / Takara Bio / Osaka University DNA vaccine In phase 1/2 study.
BioNTech (NASDAQ:BNTX) / Pfizer (NYSE:PFE)

BNT162

(Four candidates)


In phase 1/2 study.
Bharat Biotech Whole-virion
inactivated vaccine

In phase 1/2 study.
Cadila Healthcare  ZyCoV-D
In phase 1/2 study.
Clover Pharmaceuticals / GlaxoSmithKline / Dynavax  SCB-2019
In phase 1/2 study.
CSL / Sequirus / University of Queensland Molecular clamp
stabilized spike
protein with
MF59 adjuvant

In phase 1/2 study.
CureVac CVnCoV
In phase 1/2 study.
Genexine Consortium GX-19
In phase 1/2 study.
Gamaleya Research Institute Gam-COVID-Vac
In phase 1/2 study.
Imperial College London RNA vaccine
In phase 1/2 study.
Inovio Pharmaceuticals INO-4800
In phase 1/2 study.
Novavax (NASDAQ:NVAX) NVX‑CoV2373
In phase 1/2 study.
Institute of Medical Biology / Chinese Academy of
Medical Sciences
Inactivated SARS-CoV-2 vaccine
In phase 1/2 study.
Medicago / GlaxoSmithKline / Dynavax Plant-derived virus-like particle
In phase 1/2 study.
Sinopharm / Beijing Institute of Biological Products  Inactivated SARS-CoV-2 vaccine
In phase 1/2 study.
Sinopharm / Wuhan Institute of Biological Products  Inactivated SARS-CoV-2 vaccine
In phase 1/2 study.
Vaxine Pty Ltd / Medy-Tox COVAX-19
In phase 1/2 study.
Walvax Biotechnology / People's Liberation Army Academy of Military Sciences ARCoV
In phase 1/2 study.

Data sources: WHO, ClinicalTrials.gov, company press releases.

BioNTech and Pfizer reported positive results on July 1 for BNT162b1, one of four candidates in development. The FDA recently granted Fast Track designation to two of those candidates, which paves the way for an expedited review process.

Novavax has attracted a lot of attention for its COVID-19 vaccine candidate as well. Operation Warp Speed, the U.S. government's program to accelerate COVID-19 vaccine development, selected NVX-CoV2373 to receive $1.6 billion in funding.

What are the chances of FDA approval for a vaccine candidate in phase 1 testing? Very low, at least based on historical data. Only 16% of experimental vaccines in early stage studies between 2006 and 2015 ultimately won FDA approval, based on an analysis conducted by biopharmaceutical industry trade organization BIO.  

In phase 2 testing 

Two Chinese drugmakers are currently evaluating COVID-19 vaccine candidates in phase 2 clinical studies:

Organization(s)

Vaccine Candidate

Status 

Cansino Biologics / Beijing Institute of Biotechnology Ad5-nCoV In phase 2 study 
Anhui Zhifei Longcom Biopharmaceutical / Institute of Microbiology, Chinese Academy of Sciences Adjuvanted
recombinant
protein
In phase 2 study 

Data sources: WHO, ClinicalTrials.gov, Chinese Clinical Trial Registry, company press releases.

The Chinese military is already using Cansino's experimental Ad5-nCoV vaccine under a one-year special permission granted by China's Central Military Commission. The vaccine candidate isn't approved for use outside of military personnel at this time, though.

Neither of these two COVID-19 vaccine candidates is being tested in the U.S. at this point. The odds an experimental vaccine in a phase 2 clinical trial will eventually win FDA approval is low, based on BIO's historical data -- less than 25%.

In phase 3 testing (or soon will be)

There are three leaders in the COVID-19 vaccine race based on the clinical progression of their respective candidates. Each of these companies' COVID-19 vaccine candidates is either in phase 3 clinical studies or soon will be.

Organization(s)

Vaccine Candidate

Status 

AstraZeneca (NYSE:AZN) / University of Oxford AZD1222 In phase 2/3 study
Moderna (NASDAQ:MRNA) asdf mRNA-1273 Phase 3 study scheduled to begin on July 27, 2020
Sinovac Biotech CoronaVac Phase 3 study scheduled to begin in July 2020

Data sources: WHO, ClinicalTrials.gov, company press releases.

Moderna's COVID-19 vaccine program has received the most publicity in the U.S. The biotech recently announced the publication of results from a phase 1 study of mRNA-1273 in The New England Journal of Medicine. Those results showed that Moderna's COVID-19 vaccine candidate produced neutralizing antibodies (which can prevent viral infection) in all 45 participants in the study. 

It's not surprising that Moderna ranks as a big winner among biotech stocks in 2020. So far this year, Moderna's shares are up well over 300%.

Chinese drugmaker Sinovac reported in June that its COVID-19 vaccine candidate CoronaVac produced neutralizing antibodies in over 90% of patients in a phase 1/2 clinical study. Results from a phase 1 study of AZD1222, the COVID-19 vaccine candidate being developed by AstraZeneca and the University of Oxford, are expected to be published on July 20 in The Lancet medical journal.

It's still too soon to know whether any of these vaccine candidates will be successful in late-stage testing. However, 74% of experimental vaccines that made it to phase 3 clinical trials between 2006 and 2015 went on to win FDA approval, according to BIO.