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Science  —  11 minutes

Vaccine against COVID-19: Why does it take so long?

April 28th, 2020
Dr Nicolas Tétreault, Clinical Biochemist, Ph.D., FCACB, CSPQ
Dr Nicolas Tétreault, Clinical Biochemist, Ph.D., FCACB, CSPQ
Scientific and Innovation Director

With more than half of the world’s population living under lockdown, there are encouraging signs in a number of countries as a result of these efforts. Discussions are underway to begin a “certain” return to normal. Indeed, too quick a return to the pre-COVID-19 lifestyle could lead to a resurgence in infections, which would put severe pressure on health care systems worldwide.

So the question on everyone’s lips is: how soon can we expect a “real” return to normal? At the moment, no one can answer this question with certainty. Estimates are sometimes pessimistic. For example, a group of researchers at Harvard University estimates that social distancing measures will not be fully lifted until 2022.[1]

On a more positive note, many experts believe that we could eradicate COVID-19 much sooner if we find a vaccine. Given the success of vaccination, one of the greatest achievements of modern medicine, it is entirely reasonable to think that this type of treatment could protect us from infection by the SARS-CoV-2 virus and put an end to the pandemic.

Early successes in vaccination

Although immunization practices have existed for centuries, the work of Edward Jenner in the early 18th century is considered the first successful vaccination that would ultimately lead to the eradication of smallpox in 1979. With a 30% mortality rate, this is one of the deadliest diseases in human history. An estimated 300 million people died from it in the 20th century alone.[2] Vaccination has therefore made it possible to defeat this more than 3,000-year-old scourge. Since then, millions of lives have been saved with vaccines against polio, measles, diphtheria, whooping cough and tetanus, diseases that were once very common.

Aiming for herd immunity

The only way to stop the spread of the virus is to achieve herd immunity. This happens when a sufficient number of people have been exposed to the virus and recovered from it. They are then immune and, in theory, can no longer contract or transmit the virus.

With SARS-CoV-2, an estimated 70% of the population needs to be immunized to achieve herd immunity.[3] There are two ways to do this: naturally or with a vaccine. Since the natural way could be a lengthy and costly strategy in terms of deaths, vaccination is the preferred option. For this reason, enormous efforts are being made worldwide.

However, we need to be patient. The wait could last from 12 to 18 months, and success is not guaranteed. Considering that we have been producing vaccines since the 19th century, that many pharmaceutical companies have made this project a priority, and that there is a great deal of funding, why are we not seeing faster results?

Many remember that in 2009, during the H1N1 pandemic, a vaccine was available within about six months. In fact, the first official case was reported in April 2009 in North America and, in the United States, vaccination began in October of the same year.[4] Why is it different with SARS-CoV-2?

Limited expertise

The main difference between the H1N1 and COVID-19 pandemics lies in our knowledge of these two families of viruses. The influenza virus responsible for H1N1 caused three pandemics in the 20th century, which are estimated to have killed between 20 and 50 million people (the Spanish flu in 1918-1920, the Asian flu in 1957-1958 and the Hong Kong flu in 1968-1969).[5] As a result, we know a great deal about this virus, especially since we have to defend ourselves year after year against the seasonal infections it causes. For more than 65 years, the influenza monitoring system of the World Health Organization (WHO), which keeps track of the various flu virus strains circulating around the world, has been choosing the composition of the seasonal flu vaccine. So we know how to fight it, and many pharmaceutical companies are well equipped to produce vaccines quickly.

SARS-CoV-2, on the other hand, is a virus of the coronavirus family. Four viruses of this family are constantly circulating and infecting humans. An estimated 5-10% of upper respiratory tract infections are due to common coronaviruses.[6] However, the risk of complications is so low that few programs were devoted to developing a vaccine. This situation changed with the arrival of SARS (SARS-CoV-1) in 2003, and then MERS (MERS-CoV) in 2012, which had mortality rates of 10% and 37% respectively.[7] At that time, plenty of effort was put into developing a vaccine, but these programs were either abandoned or greatly reduced because outbreaks could be contained fairly quickly. Global expertise in making vaccines for this family of viruses is very limited, a situation that does not help speed up the process.

The many steps involved in making a vaccine

Lack of knowledge about the COVID-19 virus slows the process, but it is mainly the very nature of the vaccine development process that adds to the delay. Although 12 to 18 months seems like an eternity today, it normally takes more than 10 years to go through the various stages of development.[8]

Clinical phases of vaccine development

Phases Trials Duration
Preclinical Testing on animals Two years or less
1 Tests on less than 100 people to see if side effects occur 12 to 18 months
2 Trials on hundreds of people to monitor for side effects and optimize the dosage and number of injections. 2 years or more
3 Trials on thousands of people exposed to the virus to assess the effectiveness of the vaccine’s protection (duration of immunity) About five years

Regulatory approvals and the production of vaccine doses follow these clinical phases. These next steps can significantly influence the total time it takes to develop a vaccine that is ready for the population.

When researchers pick up the pace

Despite our limited knowledge of SARS-CoV-2 and the lengthy process of developing a vaccine, researchers have made significant strides so far. Never in the history of biological sciences have we seen such a concerted effort. Every day, researchers are learning more and more about this new pathogen. They are beginning to better characterize its behaviour, strengths and weaknesses. And they have already succeeded in developing vaccination formulas.

As of April 8, 2020, there were more than 115 vaccine candidates, five of which have officially entered clinical trials[9], and the list is growing by the week. To accomplish this, researchers have relied on data collected and shared around the world, and have also redesigned the development process to speed up certain steps or carry them out in parallel, instead of waiting for one step to be successful before moving on to the next.

A striking example is the company Moderna, which managed to move to phase 1 just 10 weeks after the genetic characterization of SARS-CoV-2, an unprecedented feat. In this case, animal testing was conducted at the same time as phase 1.

Another noteworthy example is the Jenner Institute at Oxford University in England, where researchers plan to produce millions of doses of vaccine by September 2020. They plan to do this by manufacturing the vaccine in large quantities before the results of clinical trials are available. In other words, the British government will fund the production of a vaccine whose effectiveness is not yet known. It’s a risky gamble, but one that would produce an injectable vaccine in six months.

Of course, developing an effective vaccine depends on identifying a safe vaccine formulation that provides immunity over a relatively long period of time. At this time, it is impossible to say beyond doubt that this can be done, especially when we consider the immunity that humans develop after infection with a common coronavirus. Infected people develop antibodies, but even those with a high level of antibodies can be re-infected. In contrast, the situation appears to be different with the coronavirus that caused SARS in 2003. Infected and cured people are believed to be protected from further infection.[10] Consequently, there is every reason for hope.

While we wait for the vaccine

To limit the number of deaths, extremely large sums of money are being invested around the world to develop new drugs against the virus, and a number of clinical trials are now underway to test the effectiveness of certain drugs already in our therapeutic arsenal to treat COVID-19. An example close to home is the COLCORONA study, being conducted at the Montreal Heart Institute, to determine the effectiveness of colchicine, an anti-inflammatory drug widely used in cardiology.

The COLCORONA study is actively recruiting. If you have tested positive for COVID-19, you may be eligible to participate. To learn more:

We are witnessing, and will continue to witness in the coming months, all kinds of advances that will help protect humanity from COVID-19 and future pandemics.

Unfortunately, collateral damage from the coronavirus crisis can already be seen. On March 26, the WHO recommended that mass immunization programs be stopped in order to protect health care professionals. The result is that millions of children, particularly in developing countries, will not receive the vaccines that protect them from a number of serious diseases such as measles, cholera and polio.[11] In this context, it is more urgent than ever to find a vaccine.

Biron offers molecular screening and serological test for COVID-19. Unlike the serological tests, the molecular screening does not require a doctor’s prescription. For more details, click here.

  1. Stephen M. Kissler, Christine Tedijanto, Edward Goldstein, Yonatan H. Grad et Marc Lipsitch, “Projecting the transmission dynamics of SARS-CoV-2 through the postpandemic period,” Science, April 14, 2020,
  2. World Health Organization, “Smallpox: eradicating and ancient scourge,” Bugs, drugs & Smoke, 2011,
  3. Gypsyamber D’Souza et David Dowdy, “What is herd immunity and how can we achieve it with COVID-19?” Bloomberg School of Public Health Insights, Johns Hopkins University, April 10, 2020,
  4. Centers for Disease Control and Prevention, “2009 H1N1 Pandemic Timeline,” (accessed April 19, 2020).
  5. Institut national de santé publique, “En savoir plus sur l’influenza,” (accessed April 19, 2020).
  6. Kenneth McIntosh, “Coronaviruses,” UpToDate, February 18, 2020,
  7. Chaolin Huang et al., “Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China,” The Lancet, January 24, 2020,
  8. Esther S. Pronker et al., “Risk in Vaccine Research and Development Quantified,” Plos One, March 20, 2013,
  9. Tung Thanh Le et al., “The COVID-19 vaccine development landscape,” Nature Reviews Drug Discovery, April 9, 2020,
  10. Ewen Callaway, “Coronavirus vaccines: Five key questions as trials begin,” Nature, March 18, 2020,
  11. Leslie Roberts, “Pandemic brings mass vaccination to a halt,” Science, April 10, 2020,
Dr Nicolas Tétreault, Clinical Biochemist, Ph.D., FCACB, CSPQ
Dr Nicolas Tétreault, Clinical Biochemist, Ph.D., FCACB, CSPQ
Scientific and Innovation Director
Having practiced in the public and private networks while constantly monitoring the evolution of biomedical laboratory medicine, Dr. Tétreault, a clinical biochemist, stands out for his innovative vision and unique expertise in the Canadian, American and European markets. He teaches at the Université de Montréal and regularly publishes texts intended for the general public or experts in the field.