- To speed up the production of a COVID-19 vaccine, manufacturers will produce doses even before last-stage clinical trials are complete.
- This is no guarantee that the vaccine will work.
- If it proves to be safe and effective, the public can be quickly vaccinated.
Even before late-stage clinical trials are finished, the United States plans to order millions of doses of a promising COVID-19 vaccine candidate, Dr. Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases (NIAID) and a member of the White House Coronavirus Task Force, said Tuesday.
“By [the end of the year] we hopefully would have close to 100 million doses, and by the beginning of 2021, we hope to have a couple of hundred million doses,” said Fauci during a live Q&A with the Journal of the American Medical Association.
However, this is no guarantee that the vaccine will work. But if it later proves to be safe and effective, the public can be quickly vaccinated.
Pharmaceutical company AstraZeneca announced that it plans to follow a similar strategy.
The company aims to distribute 2 billion doses of a COVID-19 vaccine worldwide starting in September or October, adding that this timeline depends on clinical trials taking place by August.
Late-stage vaccine trials starting soon
While the government and vaccine makers will be taking a risk by producing a vaccine early, their decision will be based on some data, even if not the full phase III clinical trial data.
Dr. Davey Smith, head of the division of infectious diseases and global public health at UC San Diego School of Medicine, says statisticians routinely review data throughout a clinical trial.
Using that, they can estimate whether a treatment, or in this case a vaccine, will likely work.
“If the probability is looking good, there may be a trigger within that trial to say, let’s go ahead and take the risk of making a vaccine that may or may not work,” said Smith, who’s not involved in the COVID-19 vaccine trials.
However, phase III clinical trials will still need to be completed before any COVID-19 vaccine can be made widely available.
“Until the [phase III] trial is over, you won’t have complete certainty whether or not the vaccine works, or if there are still some lingering safety issues,” Smith said.
Fauci said a vaccine candidate made by biotech company Moderna in partnership with the NIAID should enter a phase III clinical trial by mid-summer, with testing sites in the United States and other countries.
This trial will involve about 30,000 people. The vaccine will be tested mainly in people ages 18 to 55, but Fauci said the trial will also include older adults and people with underlying health conditions.
Once people are given the test vaccine, scientists will have to wait for them to be exposed to the new coronavirus before they will know whether the vaccine is effective.
How long this takes depends on how many infections are in the communities where those people live.
Fauci said if many participants live in areas “where you’ve had a big outburst or a surge of cases, you could get your answer pretty quickly.” Otherwise it could take months.
Questions remain about duration of vaccine immunity
Fauci is “cautiously optimistic” that with multiple vaccine candidates being developed using different platforms, we’ll eventually have an effective COVID-19 vaccine.
However, Dr. Patrick Soon-Shiong, CEO of biotech companies ImmunityBio and NantKwest, says the big question is the duration of immunity produced by a vaccine.
When people develop antibodies to the common cold virus — which is caused by other coronaviruses — the protection usually lasts less than a year. So, people may need to get vaccinated against COVID-19 every year, as with the flu vaccine.
Soon-Shiong adds that it’s not just the vaccine platform that matters for the durability of immunity, but also which part of the virus that’s being targeted.
Currently, researchers have focused on developing vaccine candidates that produce antibodies to one part of the new coronavirus called the spike protein. ImmunityBio has taken a different approach.
“There is no other vaccine developer that’s gone beyond just using spike, other than us,” Soon-Shiong said.
The company is using a second-generation human adenovirus platform to target both the spike protein and the nucleocapsid protein, which is involved in replication of the virus.
The company’s vaccine candidate has been selected for the White House COVID-19 vaccine development program, Operation Warp Speed.
It plans to begin phase I clinical trials of the candidate vaccine in June, with capacity to produce 100 million doses by the end of the year.
Soon-Shiong says having just humoral immunity, or antibodies, may not be enough to produce long-term protection against COVID-19. But targeting the nucleocapsid protein at the same time may lead to longer lasting T cell immunity.
Some studies have found that people who recovered from SARS in 2003 still have memory T cells, which are reactive to the nucleocapsid protein of the SARS virus.
“That is the impetus for us to target cell-mediated immunity,” Soon-Shiong said.
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