More than half a year into the mission to vaccinate the world against covid-19, we are getting a picture of how well each vaccine is working. We round-up what the latest research says on efficacy at preventing symptoms, hospitalisation, and death, as well as side effects, plus the latest thinking on coronavirus variants and booster shots, for all the leading vaccines: Oxford/AstraZeneca, Pfizer/BioNTech, Moderna, Johnson & Johnson, Covaxin, Sputnik V, Sinovac, Sinopharm, and CanSino.
We also take a look at the vaccines currently in trials that may be used in future, plus what we know so far about vaccination and long covid.
Ěý
Advertisement
Oxford/AstraZeneca
How does it work?
A chimpanzee cold adenovirus has been genetically altered so it can no longer reproduce and has had a gene added that encodes the coronavirus’s spike protein. When injected, the virus is taken up by immune cells, which then make the spike protein and “display” it to other immune cells, triggering an immune response.
Where is it made?
Most UK stock is made by AstraZeneca facilities in the UK, although the vaccine is also manufactured in 14 other countries. The UK has used about 5 million doses from the Serum Institute of India, but exports stopped when covid-19 surged in India earlier this year.
Are the UK and Indian versions of the vaccine different?
They are identical, but a few people in the UK who got the Indian-made version have had their covid-19 vaccine passports rejected by some European countries, such as Malta, Cyprus and Portugal. That is because the European Medicines Agency is still considering AstraZeneca’s request to approve the Serum Institute of India as a manufacturing site. The Indian-made version has batch numbers 4120Z001, 4120Z002 and 4120Z003, which can be found on UK vaccination cards or via the National Health Service app.
Where has it been approved?
It has various forms of approval in 121 nations, including the UK, Australia, New Zealand, Canada and those in the European Union.
How many doses have been distributed so far?
More than a billion doses have been manufactured.
Are there side effects?
All vaccines can cause a sore arm and issues including fever, fatigue, dizziness and headache. The Oxford/AstraZeneca one has also been found to rarely cause a blood-clotting syndrome called vaccine-induced immune thrombotic thrombocytopenia, or VITT.
This tends to occur more often in younger people: it is estimated to happen after 1 in 100,000 doses . Because of this, some countries, including the UK, are limiting the vaccine’s use in younger age groups.
How effective is it?
Figures from Public Health England suggest it is 75 to 99 per cent effective at reducing deaths from covid-19 after two doses. Having two shots reduces the number of people who need to go to hospital because of the virus by between 80 and 99 per cent and cuts the number who have an infection by 65 to 90 per cent. One dose is estimated to reduce transmission by 35 to 50 per cent, but there are no figures yet on how much it reduces transmission after two doses. However, all these figures date from a time when the main coronavirus variant in the UK was alpha (formerly known as the Kent variant).
How long does immunity last?
We don’t know yet, but the UK is considering offering booster vaccinations from September to vulnerable groups and people aged 50 or over.
How effective is it against variants?
Two doses seem to be 67 per cent effective , originally spotted in India. That compares with 75 per cent effectiveness against the alpha variant but only , which was first seen in South Africa.
Ěý
Pfizer/BioNTech
How does it work?
The vaccine uses messenger RNA (mRNA) to make the body produce a protein from the coronavirus and prime your immune system to fight off the real thing.
Where is it made?
The manufacturing process involves multiple sites, but most doses are distributed from sites in Kalamazoo in Michigan and Puurs in Belgium.
Where has it been approved?
It has forms of approval in 97 countries so far, including the US and the UK, which was the first country in the world to authorise it.
How many doses have been distributed so far?
“Hundreds of millions of doses,” according to Pfizer.
Are there side effects?
The most common is pain at the injection site, followed by fatigue and headache. More serious side effects, like severe allergic reactions or heart inflammation (myocarditis), have been reported, but are extremely rare.
How effective is it?
±Ę´Úľ±łú±đ°ů’s found that it was 95 per cent effective at preventing symptomatic disease. There is less information on asymptomatic cases, but one study found that the vaccine cut these by about a third in those over 60.
A in June found that it is 89 per cent effective at preventing hospitalisation and 100 per cent effective at preventing the need for admission to an intensive care unit.
Two , found that two doses of the vaccine were 80 to 88 per cent effective against infection and 41 to 79 per cent effective at cutting transmission. The latter range is uncertain because so few vaccinated people infected others, so the sample size was small.
How long does immunity last?
The vaccine is still strongly effective at preventing disease six months after the second dose, but the efficacy does slowly decline, according to a preliminary Pfizer . In the first two months after the second dose, efficacy against disease was 96 per cent, but by four to six months it had fallen to 84 per cent. The study ended before the delta variant had become so dominant.
How effective is it against variants?
The vaccine held up well against the alpha variant, but we know less about its performance against delta. One UK suggested that one dose was 31 per cent effective against symptoms caused by delta and two doses were 88 per cent effective.
Preliminary suggests the vaccine is also less able to prevent transmission of delta. The country has begun giving a third shot as a booster to people aged over 60.
According to a Pfizer , there is evidence that a third dose given at least six months after the second can boost antibodies against the delta variant at least fivefold.
Ěý
Moderna
How does it work?
Like the Pfizer/BioNTech jab, the Moderna vaccine uses messenger RNA (mRNA) that prompts the body to produce a protein from the coronavirus that then primes the immune system.
Where is it made?
At a plant in Norwood, Massachusetts.
Where has it been approved?
It has various forms of approval in 64 countries.
How many doses have been distributed so far?
Moderna’s initial agreement with the US government was for 100 million doses. The firm expects to supply 800 million to 1 billion doses globally in 2021 and up to 3 billion in 2022.
Are there side effects?
The vast majority are mild and short-lived, such as headache, nausea and swelling of the underarm glands on the side that was injected. Heart inflammation, or myocarditis, occurs very rarely.
How effective is it?
Moderna’s initial analysis, released in November 2020, found that two doses were 95 per cent effective against symptomatic disease.
This is backed by an co-authored by Venky Soundararajan, co-founder of nference, an AI biomedical start-up in Massachusetts, published in June. It found that the vaccine was 93 per cent effective against infection, whether symptomatic or asymptomatic.
Moderna’s initial analysis found that the vaccine was 100 per cent effective against severe disease, while Soundararajan’s study found it was 86 per cent effective against hospitalisation and 100 per cent effective against admission to an intensive care unit.
The World Health Organization says it isn’t clear if the vaccine prevents transmission. However, a recent by Marc Lipsitch and Rebecca Kahn at Harvard University concluded it does. They estimated that one dose of the Moderna vaccine reduces the potential for transmission by at least 61 per cent.
How long does immunity last?
A published in April found that antibody levels remained high six months after vaccination. That same month, Moderna after a jab. This suggests that the protective effect doesn’t decline much in the first six months.
How effective is it against variants?
Moderna released a addressing this question. There was no difference in antibody levels produced against the alpha variant and the original virus. However, the beta, delta and gamma variants did show reductions. Levels were 2.1 times lower for delta, a drop the company describes as “modest”.
Will a booster shot be necessary?
It is distinctly possible and Moderna is preparing to roll out such shots. It has developed a booster that targets the beta variant, which shows some evidence of escaping immunity. In a , the company found that antibody levels against beta were low in people vaccinated six months earlier, but that the booster brought levels back up to the original post-vaccine peak.
Ěý
Johnson & Johnson
How does it work?
The Johnson & Johnson vaccine is similar to the Oxford/AstraZeneca one in using a harmless adenovirus that has been tweaked so it can no longer reproduce. But the Johnson & Johnson one involves a human virus, not a chimpanzee one. The virus has been given a gene that encodes the coronavirus’s spike protein, which prompts our immune cells to make the protein and trigger an immune response.
Where is it made?
The Netherlands and the US.
Where has it been approved?
It has various forms of approval in 59 countries, including the UK and the US.
How many doses have been distributed so far?
The US Centers for Disease Control and Prevention (CDC) estimates that more than 13 million doses have been given in the US.
Why do you only need one dose?
Johnson & Johnson tested this vaccine giving just one dose in its final-stage clinical trials, because the initial small trials suggested that this gave a strong-enough immune response. The firm also has a trial ongoing testing two doses given eight weeks apart, an approach that is likely to raise the immune response still further and make it last longer.
Are there side effects?
The vaccine has been found to rarely cause the same blood-clotting syndrome, called vaccine-induced immune thrombotic thrombocytopenia, or VITT, as the Oxford/AstraZeneca vaccine. In the US, 28 such cases of VITT were identified after nearly 9 million doses had been given. The CDC paused use of the vaccine in April as a result, but allowed it to restart after 10 days.
How effective is it?
There is less real-world data available for this vaccine than for several of the others, but its . There were no hospitalisations or deaths during the trial.
How long does immunity last?
It isn’t yet known how long immunity lasts.
How effective is it against variants?
A . The study authors say a second dose of the Johnson & Johnson vaccine may be beneficial.
Ěý
Covaxin
How does it work?
Covaxin is an inactive vaccine, comprising the coronavirus that causes covid-19, but in an altered form that can’t replicate. When the vaccine is injected into the body, the immune system learns to recognise the virus.
Where is it made?
It is produced by Bharat Biotech in India.
Where has it been approved?
India approved emergency use of Covaxin in January. Eight other countries have given it various forms of approval, but the US Food and Drug Administration says there is insufficient information for it to grant approval. The World Health Organization is expected to make a decision soon.
How many doses have been distributed so far?
The exact numbers are unclear, but fewer have been distributed than had been hoped. The Indian government says it anticipates receiving 400 million doses between August and December this year, but Bharat Biotech has so far delivered only 16 million shots, missing its target of 80 million jabs between January and July.
Are there side effects?
For several days, there may be a few side effects of Covaxin, including fever, headaches, irritability and pain or swelling on the injected arm.
How effective is it?
, phase III trial data shows that Covaxin has 93 per cent efficacy against severe illness. Overall vaccine effectiveness against symptomatic infections is 78 per cent and 64 per cent for asymptomatic infections.
How long does immunity last?
It isn’t known yet how long the body’s immune response to Covaxin lasts.
How effective is it against variants?
Blood serum analysis by the US National Institutes of Health .
However, some research suggests that Covaxin stimulates about 2.7 times fewer neutralising antibodies against the delta variant and three times fewer against the beta variant.
Similarly, the vaccine is reportedly effective , but with a weaker immune response to this variant.
Will a booster shot be necessary?
We don’t know yet. Bharat Biotech is conducting trials on booster shots and is due to release the first results in August.
It is possible that booster jabs may be needed annually to keep antibody levels high enough to protect people.
Ěý
Sputnik V
How does it work?
The Sputnik V vaccine uses tweaked adenoviruses, like the Oxford/AstraZeneca and Johnson & Johnson vaccines. But unlike in the others, the inactivated viruses used to deliver dose one and dose two of Sputnik V are slightly different, which theoretically makes the immune response it provokes stronger.
Where is it made?
The vaccine was developed by a team at the Gamaleya National Center of Epidemiology and Microbiology in Moscow with funding from RDIF, Russia’s sovereign wealth fund. It is manufactured in Russia by pharma companies part-owned by RDIF, and also under licence in 14 other countries.
Where has it been approved?
It is available in 69 countries with a combined population of 3.8 billion, mostly on an emergency use basis. The vast majority of these are low-income countries.
There is also “Sputnik Light”, which is just the first dose, for use in places with acute outbreaks in need of rapid vaccination. This is approved in 12 countries.
How many doses have been distributed so far?
According to database company Statista, Russia has exported more than 600 million doses – 250 million of them to India – and a further 3.3 billion doses have been manufactured abroad under licence.
Are there side effects?
The vaccine is well tolerated: just over half of people given both doses had mild side effects such as headache, flu-like illness and sore arms. RDIF has said that real-word findings from and .
How effective is it?
RDIF has , citing non-peer-reviewed numbers from and the .
In February, a peer-reviewed analysis against moderate or severe disease, both from the day of dose two onwards.
The first dose alone, as is administered as Sputnik Light, is 79 per cent effective at preventing infection, according to The Lancet paper. An .
How long does immunity last?
There is no data on duration, but it has been .
How effective is it against variants?
Very effective, according to research done at the Gamaleya centre and published in the journal Vaccines , beta, delta and gamma variants.
However, a very small .
China’s coronavirus vaccines
IN TERMS of sheer numbers, the leading Chinese vaccine is the snappily named BBIBP-CorV from Beijing-based pharmaceutical firm Sinopharm and the Beijing Institute of Biological Products. This is an inactivated virus vaccine that uses viruses originally isolated from covid-19 patients in China. These are grown in cell culture and then “killed” by soaking them in a chemical called beta-propiolactone.
This vaccine is approved in some form in 59 countries, mostly low-income ones, and also has emergency use listing from the World Health Organization (WHO), which means it can be used under COVAX, the global initiative for equitable vaccine sharing.
Information from Sinopharm is thin on the ground, but the WHO says that all the vaccines on the emergency use list are “highly effective in preventing severe disease and hospitalisation due to covid-19”. WHO approval is also an endorsement of safety.
Peer-reviewed results of a phase III trial showed that the vaccine is 78 per cent effective against symptomatic disease (JAMA, ). The WHO concluded that the Sinopharm coronavirus vaccine is 79 per cent effective against hospitalisation.
The vaccine seems to be effective against the alpha coronavirus variant but less so against the beta variant. Peer-reviewed data on its effect on the gamma and delta variants has yet to emerge. The WHO says there is also no information available on whether it prevents transmission.
Another inactivated virus vaccine from China, Coronavac from Sinovac Biotech, has some form of approval in 39 countries, mostly low-income ones, and has WHO emergency use listing.
Efficacy of this vaccine varies a lot from trial to trial, with a high of 84 per cent against symptomatic disease in a trial in Turkey and a low of just over 50 per cent in Brazil. The WHO’s emergency use listing assessment concluded that the vaccine is 51 per cent effective at preventing symptomatic disease but 100 per cent effective against severe disease and hospitalisation.
Effectiveness against variants also varies. Some research suggests the Sinovac vaccine works well against the alpha variant but less so against beta, and is ineffective against gamma. However, the WHO says it is effective against gamma. There is no data on its efficacy against delta. The WHO also says there is no information available on whether it prevents transmission.
A third Chinese vaccine, Ad5-nCoV from CanSino Biologics, is approved in eight countries but not by the WHO. It uses an adenovirus as a parcel to deliver the DNA for the coronavirus spike protein into the body, given as a single dose. Results from a trial in Pakistan suggest 66 per cent effectiveness.
Three other Chinese vaccines are being used exclusively in China, and one is in use in China and Uzbekistan. One of these vaccines was also developed by Sinopharm, in partnership with the Wuhan Institute of Virology. It is essentially identical to BBIBP-CorV and just as effective, but used a different SARS-CoV-2 sample as its starting point.
Ěý
The ones that got away
A few coronavirus vaccines have fallen by the wayside, but not many. Of a total of 135 candidates, just five have been abandoned. Given that around three-quarters of experimental vaccines usually fail, that might seem very low, but there is still ample time for more to fail. None of the vaccines have secured full regulatory approval in the US or UK yet.
Three of the failures involved a technology called replicating viral vector (RVV), which uses a live, replicating virus unrelated to the SARS-CoV-2 coronavirus to deliver SARS-CoV-2 genes. All produced disappointing results in early trials.
None of the 21 approved vaccines are based on this technology, so it is tempting to view it as a failure, but it has succeeded with other diseases and there are eight coronavirus RVV vaccines still in clinical trials.
One of the other failures, from Imperial College London, used a novel self-amplifying mRNA technology. Progress simply proved too slow.
The other one, a protein subunit vaccine from the University of Queensland, Australia, also tried and failed to push the technology envelope. One of its components was a protein derived from HIV that helped to stabilise the SARS-CoV-2 spike protein. But this unexpectedly caused some volunteers to record false positive tests for HIV, which could interfere with legitimate results from such tests.
Ěý
More in the pipeline
Several further coronavirus vaccines are in late-stage testing. According to McGill University’s vaccine tracker, there are 130 coronavirus vaccines still in clinical trials, 40 of them in phase III.
In the UK, those most likely to see the light of day are made by Novavax, Valneva and CureVac. The UK government has options to buy batches of all three, pending approval.
Novavax’s shot consists of spike proteins from the SARS-CoV-2 virus embedded in a virus-like nanoparticle. Interim results from phase III trials suggest it is about 90 per cent effective at preventing disease with the original coronavirus strain but less effective with variants (NEJM, ). Novavax is tweaking the vaccine to deal with them.
Valneva’s vaccine is an inactivated virus vaccine, the only one of its kind in development in Europe. It is in a phase III trial in the UK, with results expected in September.
CureVac’s jab is an mRNA vaccine, but results from its phase III trials so far have been disappointing, with only 48 per cent efficacy against infection.
Other late-stage vaccines worth watching are from the Canadian firm Medicago, which grows vaccines in a relative of the tobacco plant, as well as a viral protein vaccine from pharma giants Sanofi and GlaxoSmithKline. Initial results on the latter disappointed and trials were halted, but it has been reformulated and is showing promise in phase III trials.
Ěý
Do vaccines affect long covid?
Being vaccinated reduces your chance of getting long covid, which can involve a variety of symptoms that persist for weeks or months after an infection with coronavirus.
The benefits of vaccination in reducing the risk of getting long covid can be seen even if people get infected after having a shot. There is also evidence that vaccines reduce the severity of symptoms in most people who already have long covid, but in a minority their symptoms worsen.
While various studies are getting under way, so far there is almost no published evidence on the relationship between long covid and vaccination.
“We do not yet know to what extent covid-19 vaccination can prevent long covid,” says at the University of Oxford, whose team will use data from the UK’s National Health Services to try to answer this question.
A team at King’s College London has released initial findings from an ongoing study in which people report any long covid symptoms via an app. According to study leader , vaccination reduces the risk of getting long covid by a factor of 20 (medRxiv, ). This is mainly because vaccination reduces the risk of being infected in the first place by a factor of 10, and the risk is also halved in those who get infected despite being vaccinated, says Spector.
For those who already have long covid, it seems vaccination can be helpful. In a survey of 900 people who were vaccinated after having symptoms lasting for at least four weeks and in most cases more than three months, around 60 per cent reported an overall improvement in their symptoms. A quarter reported no difference and 20 per cent reported worsened symptoms (SSRN, ).
“Ours is the largest study and probably the best evidence to date,” says at LongCovidSOS, a UK organisation that campaigns for support for people with long covid.
Of the three vaccines that Sherwood and her colleagues assessed, the Moderna one was most beneficial, reducing the average symptom severity score by 31 per cent. For Pfizer/BioNTech, it was 24 per cent, and 23 per cent for Oxford/AstraZeneca.
Sherwood and her team want to do a follow-up to see how long the symptoms last and what the impact of a second dose is. However, a randomised trial rather than a survey would provide more reliable results.
The different effects of vaccination on long covid make sense given emerging evidence that there are many different mechanisms that can cause long covid. It can be due, for instance, to persistent infections in some parts of the body, to tissue damage from past infection, to disruption of the immune system or can arise from all of these occurring in one person.
Vaccines would be expected to help clear persistent infections, but to make no difference to tissue damage. They might even worsen immune disruption in some cases.
