There are at the moment more than 40 vaccine trials aimed at preventing Covid-19. Even so, the most optimistic projections are that the earliest a vaccine will be ready is by Easter 2021.

It’s a critical race, since every epidemiological model shows that the virus won’t fully subside until there is a mass vaccination programme to halt infections. But making a vaccine is a field of science in which failure is almost guaranteed: more trials will crash and burn than succeed.

These are the five things you need to know about a vaccine.

1) The world has been waiting for Disease X

It is no secret that many diseases first spread from animals, causing outbreaks like Ebola, swine flu or Lassa fever. These, as well as new diseases like Zika, require vaccines, and scientists have been preparing technical platforms to create vaccines quickly for the inevitable “Disease X”.

Disease X is a term coined by the World Health Organisation (WHO) to describe the next global pandemic – even if the source couldn’t be anticipated.

SA professor Helen Rees, who chairs the scientific advisory committee of the Coalition for Epidemic Preparedness Innovation (CEPI), explains that global organisations like hers exist to develop technology so that when a new disease emerges, the technology is there to quickly produce a vaccine.

Rees describes the technology designed for vaccines as “a plug and play” model ­– scientists get the platforms ready so that when the genome of a new virus is sequenced, a vaccine can be developed within weeks. 

Soon after the mystery virus was detected last year, China released the gene sequence for SARS-CoV-2 in January. Almost immediately, CEPI and other similar organisations held numerous meetings about a vaccine.

Private companies also hit the ground running. Paul Stoffels, chief scientific officer at pharmaceutical company Johnson & Johnson (J&J), says his company has been working on a possible vaccine since January. J&J has now been selected as one of the vaccine candidates, and is currently testing it in mice. If all goes well, J&J plans to start human clinical safety trials by September 2020. 

2) Vaccines can be made very quickly

Gone are the days where scientists had to spend years to weaken the strain of a virus or bacteria before it was harmless enough to be given to humans.

Thanks to new technology, vaccines are being created that include part of the virus’s genetic material, rather than a weakened form of the virus. 

The way it’s meant to work is that the genetic code is injected into a person and the body follows the instruction to create a small part of the SARS-CoV-2 virus. This prompts the human immune system to respond and fight against the virus fragment.

The US National Institute of Allergy & Infectious Diseases (NIAID) is trialling just such a vaccine in Atlanta and Seattle. 

That NIAID trial is also using existing technology from a never-before-used vaccine that was developed against a different coronavirus that caused Middle Eastern Respiratory Syndrome (MERS). In that case, the vaccine wasn’t needed as MERS was brought under control. But the MERS vaccine technology has provided “a head start” for developing a vaccine candidate to protect against Covid-19, says trial head Dr Lisa A Jackson.

J&J is using a different technology, which builds on the vaccine research done for Zika, Ebola and HIV/Aids.

Stoffels says: “To create our SARS-CoV-2 vaccine candidate, we have removed part of the common cold genome so that the virus can no longer multiply – which created room to insert the gene encoding for a piece of coronavirus. So we have a common cold virus that, in its genetic material, holds a part of the coronavirus.”

NIAID director Dr Anthony Fauci says the Atlanta and Seattle Covid-19 trial has been done in “record speed”.

​3) Safety can’t be rushed— but it also doesn’t take that long

Today, new vaccines can be designed in weeks using existing technology. But scientists have to follow volunteers for a few months to ensure they don’t develop an allergic reaction to the vaccine.

Dr Wilbur Chen of the Center for Vaccine Development & Global Health at the University of Maryland says reactions can occur within days or after months of vaccination. As a result, volunteers are closely monitored and asked to measure any redness from the injection site and record the size and time of any swelling. Any fever or negative reaction is also documented. 

Typically, safety trials start with a few dozen people, and then shift to testing on hundreds of people. Chen says: “If there is a rare 1-in-10,000 or 1-in-100,000 event, it could be something we do not know about.” But, he adds: “Adverse events are pretty rare.”

Scientists typically make a trade-off between a rare adverse effect and the protection a vaccine provides. “We would want to balance out the benefit of a vaccine saving lives and a single rare adverse event,” says Chen.

4) No-one is hunting for a lifelong full proof vaccine

Most vaccines provide 100% protection against a disease, but in the case of Covid-19, even a vaccine that reduces the incidence of disease by 50% might be acceptable. As Kathleen Neuzil, director of the Center for Vaccine Development & Global Health at the University of Maryland, put it in a conference call with journalists: “Imagine half the people sick in New York, half needing hospitals, half of the health workers sick.”

5) This is the fastest vaccine ever made

Chen and Neuzil told journalists that vaccine development usually takes 10 years. This is, in part, because drug companies and health authorities want vaccines that protect people for at least three to four years, as vaccinating people every six months against a disease is unrealistic and costly.

Usually, studies will follow participants for years to see if the vaccine protection lasts.

 But the world is so desperate for a vaccine against Covid-19 – even if its protection wanes after six months and people need a booster shot – that this might be good enough at first. Looking for a vaccine that initially only provides temporary protection speeds up the trials. 

At this point, though, we don’t know which of the 40 trials will succeed. As Neuzil says: “There are a lot of shots on goal right now. We are hoping we will score with one of those.”

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