When several European countries paused use of the Oxford/AstraZeneca Covid vaccine in March 2021, the criticism from many commentators was swift, extreme…
It’s just over 2 and a half years since the genome sequence of SARS-CoV-2 was released, kicking off the Covid vaccine race in earnest. Remember when people were cautioning that it would take 12 to 18 months to get a vaccine? It actually only took 6 months till the first emergency use authorization for a vaccine came in China, with several vaccines in phase 3 trials globally. A few weeks later, I wrote that a clinical trial stampede had started. So how many vaccines and trials do we know of now? Let’s start with those, and a few other numbers:
- 368…. that’s how many Covid vaccines there are in development and/or use – at least
- 4.3 million…. people already participating in, or planned for, clinical trials of Covid vaccines so far
- 943…. the number of those trials (just over half of them randomized)
- 34…. the number of Covid vaccines authorized for use in at least 1 country
- 10…. vaccines authorized by WHO (and 1 of those has had supply suspended)
- 17…. the number of Covid vaccines we know have been abandoned late in development
Before we get stuck into more numbers and details, here’s an explanation of the sources I’ve used in this post. [Or jump straight to the list of contents]
I’ve used a variety of trackers. Each of them has a different purpose, and thus track somewhat different things. Even when they track the same issue, they can use different sources, or use different definitions. For example, when do you list a vaccine among those in phase 3 trial – when the trial is registered, or when the first patients are enrolled? There can be a long time between those timepoints, especially if a multi-phase trial was registered (eg phase 2/3): phase 2 can take a long time, and phase 3 isn’t guaranteed. And do you call a vaccine regimen that includes more than one vaccine type made by the same manufacturer one vaccine, or count each vaccine separately? On top of that, some people are capturing data that others miss. I haven’t tried to do a detailed data reconciliation in this post: I’m just aiming for the best estimate.
I began and maintain a collection for tracking Covid vaccine development, via public preclinical and clinical trial results. (Notes that collection are here; it’s in a public Zotero library you can dig into here.) For most of this post though, I relied on other sources that aren’t constrained by results. Those trackers are listed below, along with the date of their most recent updates:
- WHO: World Health Organization Covid vaccine landscape and tracker (August 30)
- WHO vaccine authorization: Status of vaccines (July 2022)
- VIPER tracker: developed by Nicole Basta and Erica Moodie and their team at McGill University in Canada (August 29)
- Covid-NMA: Cochrane-led living network meta-analysis initiative (August 25)
- NYT tracker: New York Times Coronavirus Vaccine Tracker, by Carl Zimmer, Jonathan Corum, Sui-Lee Wee, and Matthew Kristoffersen (August 26) [Update: This tracker will no longer be updated.]
- Wikipedia: particularly the list of authorized vaccines
I’ve broken the details down into these sections:
How Many Vaccines?
This one is surprisingly difficult to answer, with widely varying estimates. The best official estimate we have is from WHO, which reports 368 Covid vaccines – of which 198 are currently in the preclinical stage, and 170 in clinical trials.
I’ve found over 350 just with preclinical results released, so I think the actual number could be quite a bit north of 368 – many of those, though, either were never intended to be further developed, or were never particularly likely to leave the lab.
According to the WHO, the 3 most common vax types to reach clinical trials are:
- Protein subunit (32%)
- RNA (24%)
- Inactivated (13%)
As of a few weeks ago, these are the types of the 33 vaccines for which I found phase 3 results:
- Protein subunit (45%)
- Inactivated (18%)
- mRNA (15%)
- Viral vector (15%)
- DNA (3%)
- Virus-like particles (3%)
How many trials and participants?
Estimates vary a lot here, too, from NYT’s 123 vaccines in clinical trials, to WHO’s 170, and VIPER’s 222. VIPER has 775 clinical trials in 79 countries for those 222 vaccines. Part of the difference is that VIPER counts different manufacturers’ versions of the same vaccine as additional vaccines – like the Oxford vaccine produced by AstraZeneca, and the Serum Institute of India’s version called Covishield.
The biggest collection of trials in this set of trackers is at Covid-NMA, but I couldn’t figure out how many different vaccines there were. They have 943 trials, with over 4.3 million participants planned – over 2.3 million of those people for randomized trials. There are about 200,000 participants up to the age of 9.
The 11 countries with the most Covid vaccine trials according to Covid-NMA are:
- 164 trials: China
- 107: USA
- 50: Thailand
- 44: Brazil
- 42: India and Japan
- 40: Germany
- 37: Australia
- 35: Iran
- 31: Netherlands and South Africa
According to VIPER, 86 vaccines have made it to phase 3 trials. I make it 33 vaccines with at least some phase 3 results available, nearly a third of which were developed in Asia (mostly China).
How many vaccines have been authorized for use?
Wikipedia has a detailed list of 34 vaxes with authorizations in at least 1 country – but VIPER reports 37, and they all look right to me. VIPER includes additional versions of 4 of those vaccines, which makes it hard to work out how many countries have authorized distinct vaccines.
WHO has its own regulatory processes, either emergency use listing or prequalification, which enable vaccines to be used for COVAX supply and for use in UN agencies. There are 10 of those vaccines (including 1 for which supply has been suspended – Covaxin, the inactivated vaccine from Bharat Biotech, India).
According to the Wikipedia list, the vaccine that has been authorized in the most countries is the Oxford/AstraZeneca vaccine (including other versions). That doesn’t correspond to being more widely used, because that doesn’t reflect either population spread – eg China’s not one of the countries – or quantity of doses used.
VIPER has a global map showing several countries have authorized 10 or more Covid vaccines, including Hungary, India, Indonesia, Iran, Mexico, and Philippines. Iran has the most: 12 vaccines authorized.
How many vaccines have been abandoned?
We’ll never know how many vaccines fell by the wayside, or just were never intended to go the distance. The best tracking of abandoned vaccines I’ve seen comes from NYT: they list 17 vaccines, some of which were a surprise to me – I hadn’t heard that Imperial College London dropped theirs, or that Israel’s Brilife was abandoned. The list is fascinating reading. To see it, click here, scroll to Filter the list of vaccines and click the red “Abandoned” button.
Those 17 vaccines include several each of the main Covid vaccine types – protein subunits, inactivated, RNA, viral vectors – and some others as well.
Update: The day after I posted this, Zimmer tweeted that the NYT tracker will no longer be updating.
Update, September 1: Added news that the NYT tracker will no longer be updated.
Disclosures: My interest in Covid-19 vaccine trials is as a person worried about the virus, as my son is immunocompromised: I have no financial or professional interest in the vaccines. I have worked for an institute of the NIH in the past, but not the one working on vaccines (NIAID). More about me.