Coronavirus vaccines are rolling out quickly. Here's where the pipeline stands.
Scientists, drugmakers and governments have moved with unprecedented speed to develop multiple vaccines for the new coronavirus.
The fastest of them have proven their vaccines can strongly protect against COVID-19. More than half a dozen shots from developers in the U.S., U.K., Germany, China and Russia have now been cleared by regulators around the world.
Estimates of vaccine efficacy from Phase 3 clinical trials
Their success is a scientific feat with few parallels. No vaccine has ever been developed so quickly before, never mind readied for widespread use and manufactured at scale.
With the health of their citizens at stake, governments invested enormous sums of money into vaccine research and development, and to prepare to make and distribute the billions of doses necessary to curb the pandemic.
The immunization campaigns that are now underway will help determine whether the virus becomes endemic, recurring year after year, or is ultimately checked. Doses of authorized vaccines remain in short supply worldwide, however, and access has largely been dictated by lucrative deals struck between drugmakers and wealthy countries.
Vaccine frontrunners have progressed quickly
Here's where things stand for the most advanced, most promising or best-funded vaccine candidates. Use the menu on the left to jump to a developer.
One of the advantages to messenger RNA technology — a drug-making approach that uses genetic instructions to teach cells to make proteins — is that it can be used to build a vaccine more easily than traditional methods. Moderna's coronavirus vaccine is proof.
The vaccine went from a computer design in January 2020 to human study in just three months, making Moderna the first U.S. company to reach that point.
Phase 1 results came in late May, as did the start of a mid-stage trial. A Phase 3 study began on July 27 and, four months later, delivered strongly positive results that indicated the vaccine was 94% effective in preventing COVID-19.
The finding was a dramatic achievement. Taken together with a similarly positive readout from Pfizer and BioNTech, which in November said their shot was 95% effective in preventing COVID-19, researchers could be sure that mRNA vaccines were protective.
Crucially, Moderna's vaccine also appeared safe, with no unexpected or serious side effects. The company asked the Food and Drug Administration for emergency approval on Nov. 30 and a panel of agency advisers endorsed the vaccine on Dec. 17. Just one day later, the FDA granted authorization for the shot, marking a milestone for both the U.S. public health response to the pandemic and for the decade-old biotech.
Initial supplies were limited to several tens of millions of doses, although the company and its partners quickly ramped up production. On Feb. 12, the U.S. contracted to buy another 100 million doses from Moderna, bringing its total on order to 300 million.
More recently, Moderna and contract manufacturer Catalent agreed to expand their work together, dedicating a high-speed production line at an Indiana factory to the biotech's use through June 2023.
Two remaining unknowns are how long the protection from the first generation of mRNA vaccines will last, and whether they will be equally protective against virus variants first identified in South Africa and Brazil.
Though Moderna has shown evidence that its vaccine holds up for at least six months, its executives believe yearly booster shots will be necessary. The company is also pushing ahead with three different strategies to account for waning immunity and variants that may compromise protection.
Moderna is testing a third shot of its original vaccine, a booster designed to counter the South African variant and a shot combining both of them. Early results from the study on May 5 showed the first two concepts appear to work as intended, raising antibody levels against the variants, albeit not as high as they were against the original virus. The trial is ongoing.
CanSino had the distinction of being among the first to begin testing its vaccine in humans, report early data and start immunizations outside of a clinical study. But those milestones faded as the company struggled to complete a large Phase 3 trial and obtain the kind of proof regulators outside of China would need to authorize use.
Early and mid-stage trial results were sufficient to persuade the Chinese military to clear emergency use of CanSino's vaccine in soldiers last summer. Declining COVID-19 cases in China, however, pushed CanSino and other Chinese vaccine developers to seek study sites overseas.
CanSino, which has ties to Canada, originally intended to study its shot in Canada, but an agreement there came undone.
A large late-stage study is recruited volunteers in South America, Mexico, Pakistan and Russia. On Feb. 24, 2021, Cansino reported its vaccine was 65% effective in preventing symptomatic cases and 90% efficacy in preventing severe disease 28 days after a single shot. One day later, China's drug regulatory issued a conditional market authorization. The results have not been published.
Mexico and Pakistan approved the vaccine in February, Hungary authorized it in March and Chile followed in April.
CanSino's choice of vaccine design may limit the shot's potential, though. Early studies showed pre-existing immunity to the adenovirus, or viral vector, that CanSino uses to deliver its vaccine appeared to compromise its effectiveness.
Inovio has fallen behind in its development of a coronavirus vaccine, with late-stage testing stalled, no large pharma partners and little financial backing.
A partial clinical hold imposed by the FDA in late September last year kept the company from conducting further study of its vaccine candidate until mid-November, when the agency cleared a Phase 2 trial to begin.
Inovio's candidate uses DNA to coax cells to produce coronavirus proteins, thereby stimulating an immune response to protect against infection by the virus. To allow the DNA molecules to enter cells, Inovio uses a process called electroporation, a small electrical pulse that opens small pores in cells. The device used to do this was the subject of some of the FDA's concerns, which the company plans to address via the Phase 2 trial.
Inovio planned to launch a Phase 3 trial in the U.S. once those questions were resolved. But in April, the company changed its plans for that study when the federal government, citing the availability of other vaccines, pulled funding. Inovio now aims to run a large efficacy trial "predominantly" internationally.
Summary data from a small Phase 1 trial were disclosed by the company in June 2020, and published in a medical journal on Dec. 24. Vaccination was safe and spurred immune responses against the virus. Those responses appeared weaker than what was reported for Pfizer's and Moderna's shots, however.
In the U.S. and Europe, vaccine developers bet on newer technologies, such as messenger RNA or viral vectors, that, while less established, offer crucial advantages in speed. Sinovac, along with several other companies and institutions in China and India, however, have moved almost as quickly using the tried-and-true approach of inactivated virus vaccines.
Used for hepatitis A, influenza and rabies, these vaccines consist of viruses rendered uninfectious either through heat or harsh chemicals.
Sinovac wasn't the first to get going, but was able to obtain results from late-stage testing faster than several more closely tracked Western drugmakers. While initial reports of data from a study in Brazil suggested strong efficacy, later announcements put the shot's overall efficacy just over 50% — barely clearing a bar set by regulators around the world.
The higher figure, researchers in Brazil said, was from counting only COVID-19 cases that required medical assistance. Comparing protection against COVID-19 of any severity resulted in a lower number.
The incomplete disclosures added to confusion over Sinovac's vaccine, particularly as researchers running studies in Turkey and Indonesia had reported differing results.
The data was good enough for Sinovac to gain conditional approval in China on Feb. 8, though. The vaccine also has been authorized for emergency use in 21 countries, including Indonesia, Brazil, Turkey and Chile.
In April, the drugmaker claimed it had brought online enough production capacity to manufacture up to 2 billion doses a year, and said it had already delivered 200 million doses globally.
Sinovac is listed on the Nasdaq stock exchange, but trading in its stock has been halted since February 2019 — the result of a dispute with an activist investor over control of the company.
Moderna wasn't the only biotech to aggressively push forward with the promising, but until now unproven, messenger RNA technology.
Across the Atlantic, in Mainz, Germany, BioNTech started work on an mRNA vaccine for the coronavirus early on and agreed to partner with Pfizer in March 2020, joining forces with the larger drugmaker even before their legal teams had produced a contract.
The partnership turned out to be a historic one, with the two companies winning clearance from the U.K. drugs regulator for their shot just eight months later, followed quickly by authorization in Canada on Dec. 9 and an emergency clearance from the FDA on Dec. 11. Authorities in the EU granted conditional authorization on Dec. 21.
The U.K.'s decision was a world first for a coronavirus vaccine that had completed testing; earlier vaccine approvals in China and Russia were done before late-stage studies had begun.
Unlike Moderna and other frontrunners, Pfizer and BioNTech had initially advanced four prototypes, each with subtle differences, before choosing one to take into late-stage testing. A Phase 2/3 trial began on July 28 and enrolled some 44,000 volunteers over the course of three months.
Data from the trial showed a better-than-expected 95% efficacy in preventing COVID-19. Side effects are primarily injection site pain and other common vaccine reactions like fatigue and fever.
In March, real-world use of the vaccine in Israel confirmed the shot's strong protection, with data showing 97% efficacy against symptomatic COVID-19. Results also suggested vaccination helped prevent asymptomatic infection. The shot was also 100% effective in a study of 12 to 15 year-olds, a key step to broadening the eligible population beyond the current demographic of ages 16 and older.
Pfizer, in May, became the first developer to seek a full U.S. approval of a coronavirus shot. A positive FDA decision would clear its use beyond the pandemic. The pharma is projecting $26 billion in sales for the vaccine's first year on the market, which would be a record number for a pharmaceutical product.
As with Moderna’s vaccine, the spread of virus variants first identified in South Africa and Brazil raised questions about whether Pfizer and BioNTech vaccine will remain as strongly effective. Positive results released from a real-world study in Qatar indicated that the shot, while weakened by the variant, was still 75% against the South African variant and provided near-complete protection against severe disease.
Pfizer and BioNTech, like Moderna, are looking at a second booster shot as well as a variant-specific vaccine.
Pfizer and BioNTech have contracted to supply the U.S. with 300 million doses, the most recent order coming Feb. 12. Unlike others, the drugmaker didn't relied on government funding for testing and manufacturing, claiming it's been able to move faster on its own.
BioNTech did receive nearly $450 million from the German government, however, to support vaccine development — money the biotech will use to cover its share of expenses in the partnership.
When Chinese scientists made the new coronavirus' genetic sequence available in January 2020, researchers at the University of Oxford were more prepared than most.
A team there was already working on a vaccine for the virus that causes MERS, a close cousin of SARS-CoV-2. The Oxford researchers quickly adapted their work and, by last April, had started a large Phase 1 trial.
AstraZeneca signed on to help soon after, beginning efforts to prepare for manufacturing hundreds of millions of doses.
Their speed — larger studies began in May, June and September — made AstraZeneca and Oxford's vaccine among the world's leading efforts and the subject of political tug-of-wars over who would get access.
But the program hit setbacks, beginning in early September when AstraZeneca and Oxford halted testing worldwide after one participant in the U.K. study fell sick with an unexplained neurological illness. Trials in other countries resumed quickly, but the U.S. trial didn't reopen until Oct. 23.
In late November, AstraZeneca shared preliminary data from studies in the U.K. and Brazil showing its vaccine could protect against COVID-19. Yet the positive results were confusing, showing dramatically different protection rates between a larger group that received two full doses of the shot and a smaller group that was given a half dose and then a full dose.
Despite the confusion, the U.K. drugs regulator authorized the shot about a month late. The European Medicines Agency followed in late January with a conditional authorization. The agency's decision was shadowed, however, by a conflict between the two parties over supply, after AstraZeneca told the EU it would deliver fewer doses than originally planned.
More recently, more than 20 European nations temporarily paused immunizations over dozens of reports of abnormal blood clots and low platelet counts in younger vaccine recipients. On April 7, the EMA confirmed a possible link between vaccination and the events, recommending they be added to the shot's labeling as a very rare side effect. Some European countries later restricted the shot’s use to older age groups or advised younger recipients to get another vaccine. The U.K.’s vaccine safety committee, for instance, on May 7 advised people under 40 to get a different shot.
In the U.S., AstraZeneca has said it will soon file for an emergency authorization, following positive results from a large trial there. However, the filing has taken longer than originally anticipated, reportedly because of the large amount of real-world data going into AstraZeneca’s application.
The announcement of study findings on March 22 was also marred by a communications mishap after the study's monitoring board rebuked AstraZeneca for releasing out-of-date numbers. Two days later, the drugmaker updated its efficacy estimate to 76% from 79%, based on an analysis of 190 COVID-19 cases.
The British drugmaker is also searching for a new manufacturing partner in the U.S. after the federal government directed a contractor to only make a vaccine from Johnson & Johnson's vaccine after a production mix-up at a key Baltimore factory.
AstraZeneca and Oxford's vaccine is viewed as important for global immunization efforts as it can be more easily distributed and stored. AstraZeneca has also committed to sell doses more cheaply than others.
While the Western world focused on leading candidates from large multinational drugmakers, China's state-owned Sinopharm advanced two inactivated vaccines through late-stage trials and to approvals in more than a dozen countries worldwide.
Early-stage studies began last April for both of Sinopharm's candidates, data from which were published in JAMA in August and The Lancet in October, respectively. In each case, vaccination via two injections was generally well tolerated and triggered immune system responses against coronavirus proteins.
Like other Chinese vaccine developers, however, Sinopharm was forced to test the experimental shots outside of China once the virus' spread was brought under control in the country.
The company, a sprawling conglomerate and vaccine maker, turned to the Middle East and to South American for launching Phase 3 trials, the first of which began in July 2020.
A late-stage study in the UAE of one candidate, created by the Sinopharm subsidiary Beijing Institute of Biological Products, quickly enrolled and was expanded into Bahrain, Egypt and Jordan, with a target recruitment of 45,000 volunteers.
The UAE granted emergency authorization for the Beijing Institute shot in mid-September, followed by a full approval in December.
On Dec. 31, the Chinese government said it had conditionally approved the vaccine, citing new data from the Beijing Institute that put the shot's efficacy at 79%. "Millions" of doses have already been used to vaccinate healthcare workers and people who work overseas under an emergency use program, China's health ministry said.
The vaccine is now authorized in more than 20 countries. The WHO is currently reviewing data from the trial as it considers an endorsement.
Sinopharm's other shot was developed by another unit of the company, the Wuhan Institute of Biological Products, and was being studied in Phase 3 trials in the UAE, Morocco, Argentina and Peru.
Novavax, which has spent more than 30 years trying unsuccessfully to develop vaccines, is now close to getting its first authorized.
In January, the Maryland-based biotech reported results from a 15,000-volunteer U.K. trial indicating its coronavirus vaccine was about 90% effective in preventing symptomatic COVID-19 when compared to placebo. Follow-up study data in March indicated 96% efficacy against the original COVID-19 strain, and 86% efficacy against a variant first identified in the U.K.
Protection appeared much weaker, however, against a coronavirus variant originally detected in South Africa. Overall efficacy was about 49%, although that figure rose to 55% when people positive for HIV were excluded.
Novavax's work has gained broad financial support since it began development of its shot. By the end of last May, the company had won a large grant from the nonprofit Coalition for Epidemic Preparedness Innovations and started an initial clinical trial, boosting its shares nearly 9-fold in the process. In July 2020, the biotech secured support from the U.S. government, which committed $1.6 billion to fund late-stage testing of Novavax's vaccine and to buy 100 million doses.
Results from Novavax's Phase 1 study showed its vaccine spurred encouraging immune responses. Like other experimental shots, vaccination was associated with mostly mild side effects in most trial participants. The late-stage study in the U.K. began in late September, and completed enrollment in a little over two months.
Progress slowed in the U.S., with at least two delays to a Phase 3 trial that finally got underway on Dec. 28. Novavax completed enrollment of 30,000 volunteers in late February.
Novavax expects data sometime in the second quarter, after which it's planning to file for authorization in the U.S. and U.K. The company has also become one of the largest suppliers for the international vaccine alliance COVAX, finalizing a deal in May to begin delivering an expected 1.1 billion doses of the shot to low- and middle-income countries in the third quarter.
Success could turn around Novavax, which prior to COVID-19 was struggling to stay afloat, and might reshape perception of a company that started but never finished work on vaccines for SARS and MERS.
Russia approved Gamaleya's vaccine on Aug. 11, less than two months after the first studies in humans began and, critically, before large-scale trials had proved whether it could protect against COVID-19.
The approval, which was announced by President Vladimir Putin, was a significant example of how the race to develop a coronavirus vaccine came to be quickly cast in geopolitical terms.
Like the U.S., China and Europe, Russia pushed for fast development, spurring concerns that safety risks might go overlooked or crucial steps bypassed.
In the case of Gamaleya's vaccine, the government's urgency led to an approval following two small trials in just 76 volunteers. Such studies are designed to get an early sense of a vaccine's safety, as well as whether the shot spurs an immune response.
That data was published on Sept. 4 in The Lancet, showing Gamaleya's vaccine stimulated an immune response equal to that of patients who have recovered from coronavirus infections.
With help from Russia's government and sovereign wealth fund, Gamaleya got started on a late-stage trial of its vaccine in late August, as the government was already beginning to distribute the shot.
On Dec. 14, Gamaleya released detailed data from that study, which gave 22,714 volunteers either the shot or a placebo. Researchers calculated efficacy against COVID-19 as more than 91% and the data were published two months later in The Lancet.
Gamaleya also agreed to work together with AstraZeneca, pairing the special virus it uses to deliver its shot with one used by the British drugmaker, a move aimed at improving the efficacy of AstraZeneca's vaccine. The trial began at the end of February.
More than 60 countries have authorized GRI's shot, although only some have begun vaccinations. A number have agreed to manufacture it as well.
In late April, however, regulators in Brazil rejected importing the vaccine over concerns the virus used to deliver it was not appropriately inactivated. The backers of Gamaleya's vaccine criticized the decision, calling it "of a political nature."
In early March last year, the American CEO of CureVac, Daniel Menichella, joined the heads of other coronavirus vaccine developers in a meeting with President Donald Trump at the White House.
A little more than a week later, Menichella was out as CureVac's CEO and the German biotech was at the center of swirling rumors that the U.S. had sought to buy the company, or its research.
Seemingly in response, the German government invested 300 million euros in CureVac for a 23% stake. CureVac added another $500 million through private investments, an alliance with GlaxoSmithKline and an initial public offering in the U.S. Much of the proceeds are being used to develop its coronavirus shot.
CureVac's vaccine, which has also been funded by CEPI, uses messenger RNA to encode the coronavirus' spike protein, much like BioNTech's and Moderna's. Early tests showed the shot spurred an immune response against the SARS-CoV-2 virus.
Months passed before, on Dec. 14, CureVac said it was beginning a Phase 2b/3 trial that's testing a two-dose regimen, spaced four weeks apart.
On April 15, CureVac announced its trial was fully enrolled, with over 40,000 participants across Europe and Latin America. Interim data on the vaccine's effectiveness is expected by the end of June, according to the company. Previously, CureVac's chief financial officer had told BioPharma Dive that early data were anticipated by the end of March.
CureVac's program has gotten support from two large drugmakers. First, the biotech partnered with Bayer on further development and, should trials succeed, supply of its vaccine. Then GlaxoSmithKline agreed to help make 100 million more doses of the shot in 2021, as well as co-develop second-generation versions to combat future coronavirus variants.
The U.K. government is backing that effort, too, promising to help speed testing and production of vaccines targeted against new variants.
CureVac also said on April 15 that it plans to expand its COVID-19 vaccine program, with three new studies in specific patient populations "to be initiated soon."
Clover's candidate was the second protein-based vaccine to begin human testing for the new coronavirus, trailing only Maryland-based Novavax when its Phase 1 study began in mid-June.
Like the name suggests, protein-based vaccines are designed to expose the body's immune system to viral proteins. In the case of SARS-CoV-2, that's the spike protein which the virus uses to enter cells.
Protein-based vaccines are often paired with adjuvants, compounds that help boost the immune response to vaccination. Clover chose to test its candidate together with adjuvants developed by GlaxoSmithKline and Dynavax, and planned to study both in mid- to late-stage studies.
On Feb. 1, however, Clover announced it would only proceed with a trial of its vaccine and Dynavax's adjuvant, which the companies started on March 24. The partnership with GSK, Clover said, was discontinued and the planned study dropped.
The decision was unexpected, particularly as Clover had said early testing results showed both adjuvants to be safe and capable of raising an immune response.
Clover plans to enroll approximately 22,000 volunteers across Latin America, Asia, Europe and Africa. Preliminary data could come as soon as the middle of this year, the company said, depending on enrollment and COVID-19 case rates.
CEPI has provided Clover with financial muscle, pledging nearly $70 million in July to fund the Phase 1 study and prepare manufacturing capacity should the candidate succeed. The group will fund the Phase 2/3 trial and, on Feb. 1, extended a roughly $100 million forgivable loan to begin “at-risk” manufacture of the vaccine.
J&J was first among larger drugmakers to pursue a coronavirus vaccine, announcing in January 2020 plans to develop one using the same technology that underpins several other of the pharma's experimental vaccines.
Initially, J&J didn't expect to begin clinical study until September 2020, a timeline that would have previously marked record speed but in the COVID-19 age appeared more deliberate.
The pharma sped up its plans, however, securing help from the U.S. government through Operation Warp Speed. An initial study began in late July and two months later, on Sept. 23, J&J kicked off a global Phase 3 study.
J&J had planned to recruit 60,000 volunteers, but reduced its enrollment target after cases of COVID-19 began to accelerate rapidly in the U.S. during the late fall. On Dec. 17, the drugmaker announced the study had been fully enrolled with approximately 45,000 participants.
In January 2021, data from that study showed a single dose of J&J's vaccine was 66% effective in preventing moderate or severe COVID-19. Efficacy was higher among participants recruited in the U.S., but lower in volunteers in Latin American and South Africa, where more virulent variants of SARS-CoV-2 are prevalent.
Still, the company's shot has several advantages, as it can be given via one injection and shipped at normal refrigerator temperatures. On Feb. 27, the U.S. FDA granted it emergency authorization, making J&J;'s vaccine the third available in the country. European regulators followed with a conditional authorization on March 11.
Reports of cases involving dangerous blood clots near the brain combined with low platelet counts prompted the FDA and CDC to recommend pausing use of J&J;’s shot on April 13. J&J said it will delay the vaccine's rollout in Europe as a result.
The cases were few — just six out of nearly 7 million doses when immunizations were paused and 15 out of roughly 8 million as of April 22. But the symptoms were similar to a side effect linked to AstraZeneca’s vaccine, which uses a similar technology, adding to regulators' concerns.
Nonetheless, a CDC panel on April 23 voted that the benefit of protecting against COVID-19 outweighed the risk of the rare side effect, and didn't restrict the vaccine's use in any age group. The FDA quickly cleared vaccinations to continue with updated labeling to the shot's prescribing information.
J&J expects to be able to supply 1 billion doses of its vaccine, with 200 million set to go to the U.S. J&J; delivered 20 million doses to the U.S. by the end of March and expects to deliver the rest by the end of June. Europe bought 200 million doses as well, an order Catalent is helping to fill by reserving two production lines at a plant in Italy for J&J's shot.
In the U.S., the Biden administration helped to broker a deal involving Merck & Co., which agreed to help J&J; make its vaccine and fill vials for shipping. Officials expect the collaboration could expand the number of doses produced.
But production hit a setback in March and April, when a costly take over oversight of the factory, run by Emergent Biosolutions.
Sanofi and GlaxoSmithKline agreed to join forces last April, the former contributing its protein-based vaccine technology and the latter its immune-boosting adjuvants, both of which have previously been used against influenza.
From the outset, it was clear that Sanofi and GSK wouldn't be among the first to complete testing. Their initial development timeline was months behind that of Moderna, Pfizer and even Novavax, which used a similar technology.
The two companies hoped to make up for slower speed with a more potent vaccine than others, a view they attributed to their adjuvanted approach, which is meant to strengthen the body's immune response to vaccination.
In July, they locked in $2.1 billion in support from the U.S. government to back the effort.
But Sanofi and GSK's shot fell well short of expectations. Initial results from a Phase 1 study in December were so disappointing the two companies decided to advance an upgraded formulation of the vaccine, a major setback that could delay the program by as much as nine months.
A Phase 2b study of the new vaccine began in February, with a late-stage trial expected to follow in the second quarter. Should those go well, initial availability could come by the end of the year.
Despite the delay, however, the companies' efforts could still be important, given the relative ease with which their vaccine can be shipped and stored and the number of countries depending on their progress. The U.S., U.K., Europe and Canada have pre-ordered hundreds of millions of doses. So has COVAX, an international alliance aiming to equitably distribute shots to poorer nations and economies.
In March, Sanofi began testing an mRNA vaccine it has been developing with Translate Bio, starting a Phase 1/2 trial that the companies expect to deliver results by the third quarter this year. GSK, meanwhile, began a Phase 3 study of a protein-based shot with its other vaccine development partner, Medicago.
Merck arrived late to the coronavirus vaccine race, publicly announcing its efforts near the end of May. Rather than bet on newer messenger RNA technologies, Merck homed in on approaches it believed would produce immunity quickly with one shot.
But Merck's delay, surprising for one of the world's top vaccine makers, wasn't entirely due to initial caution. The pharma initially sought to partner with the University of Oxford, developer of the vaccine candidate now licensed by AstraZeneca, but was turned down, The Wall Street Journal reported in October.
Left searching for partners, Merck instead opted to buy the privately held Austrian company Themis and its vaccine candidate, as well as license another from the nonprofit group IAVI. A Phase 1/2 study of the Themis vaccine began in Belgium in early September, while a trial of the IAVI-developed shot got underway in November.
The company had argued it could make up ground on its rivals, but weaker-than-expected results from early tests led Merck to scrap development of both candidates in late January — a surprising and significant setback. Immune responses generated by both vaccines were comparatively less than what's been observed following natural infections as well as in testing of other experimental shots.
Instead, Merck said it will focus its resources on developing COVID-19 treatments, including an antiviral drug now in mid-stage testing. In February, the company agreed to help make J&J;'s vaccine and fill vials for shipping, an unusual collaboration between large drugmakers that was brokered by the Biden administration.