Related: From alcohol to virus shedding, six dos and don'ts after getting vaccinated
The long-term mixing of different Covid-19 vaccines is unlikely to be harmful – and could even provide better protection against the coronavirus, several top experts said.
Taking one type of vaccine today and a separate dose by another manufacturer a year down the line could become normal, particularly if the pandemic continues for years.
Several top scientists gave their expert view to The National as many people debate whether to take the first available shot or wait.
Although the six vaccines approved for use around the world were each tested on hundreds of thousands of people, inevitably some have a preference or have medical reasons to hold off for now.
We may well, if there are issues around people developing immunity, deliberately switch vaccines. But we need to do a lot of work before we decide
“You shouldn’t need it, but you cannot be over-vaccinated, so any risk would be very low,” said Prof Ian Jones, professor of virology at the University of Reading in the UK.
The approved vaccines were extensively tested, but it remains unclear how long the protection they offer will last.
With the vaccines released so far, a booster injection is required within weeks of the first dose, but it may be that, beyond this, a further shot is needed to sustain protection.
Prof Jones said that if a person completed two doses of one vaccine now, and took a different coronavirus vaccine a year later, there were unlikely to be any risks.
But experts said they draw a sharp distinction between that practice and that of combining vaccines within a short space of time.
Prof Paul Hunter, professor of medicine and infectious diseases at the University of East Anglia, UK, said one drug could stimulate enzymes in the liver that break down another drug, making it less effective.
“Interactions are one of the things we hammer into medical students now,” he said.
“They have to be careful.”
If a booster is needed even later on, scientists say there may be an upside to using a different coronavirus vaccine.
Known as heterologous prime boosting, this phenomenon has been seen with vaccinations against numerous diseases.
“This has been known to greatly increase both antibody and T-cell immunogenicity when performed using certain vector combinations, above repeated dosing with the same vaccine candidate,” the World Health Organisation said in a 2014 briefing document.
Using the same vaccine repeatedly can lead the immune system to target the vaccine itself, reducing its efficacy.
An example is adenoviral vector immunity. This may affect the Oxford-AstraZeneca vaccine, which is based on a harmless form of an adenovirus that normally infects chimpanzees.
The adenovirus has had DNA added so that, once it enters human cells, it causes them to produce coronavirus spike proteins.
It is the body’s immune response to these spike proteins that offers protection against the coronavirus.
But if there is an immune response against the adenoviral vector itself, spike protein production on subsequent doses is hampered, and immunity fails to improve as it should.
“This might be why the AstraZeneca vaccine is not as effective as the other vaccines,” Prof Hunter said.
“You give the second dose and ... if the body has already developed some immunity to the carrier virus, it gets destroyed before it’s had a chance to insert its payload.”
Trials are under way to find out whether protection is stronger when a person receives one dose of the Oxford-AstraZeneca vaccine and one dose of Russia’s Sputnik V vaccine, which is based on a different adenovirus.
Immunity to the vaccine is thought to be less of a problem with the two mRNA vaccines, made by Pfizer-BioNTech and Moderna.
“We may well, if there are issues around people developing immunity to the carrier and we have to give boosters in a year or so’s time, deliberately switch vaccines,” Prof Hunter said.
“But we need to do a lot of work between now and then before we decide.”
The BIO:
He became the first Emirati to climb Mount Everest in 2011, from the south section in Nepal
He ascended Mount Everest the next year from the more treacherous north Tibetan side
By 2015, he had completed the Explorers Grand Slam
Last year, he conquered K2, the world’s second-highest mountain located on the Pakistan-Chinese border
He carries dried camel meat, dried dates and a wheat mixture for the final summit push
His new goal is to climb 14 peaks that are more than 8,000 metres above sea level
CONFIRMED%20LINE-UP
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The biog
From: Upper Egypt
Age: 78
Family: a daughter in Egypt; a son in Dubai and his wife, Nabila
Favourite Abu Dhabi activity: walking near to Emirates Palace
Favourite building in Abu Dhabi: Emirates Palace
Killing of Qassem Suleimani
AIR
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The%20BaaS%20ecosystem
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Gothia Cup 2025
4,872 matches
1,942 teams
116 pitches
76 nations
26 UAE teams
15 Lebanese teams
2 Kuwaiti teams
UAE currency: the story behind the money in your pockets
Company profile
Company: Rent Your Wardrobe
Date started: May 2021
Founder: Mamta Arora
Based: Dubai
Sector: Clothes rental subscription
Stage: Bootstrapped, self-funded
Who has been sanctioned?
Daniella Weiss and Nachala
Described as 'the grandmother of the settler movement', she has encouraged the expansion of settlements for decades. The 79 year old leads radical settler movement Nachala, whose aim is for Israel to annex Gaza and the occupied West Bank, where it helps settlers built outposts.
Harel Libi & Libi Construction and Infrastructure
Libi has been involved in threatening and perpetuating acts of aggression and violence against Palestinians. His firm has provided logistical and financial support for the establishment of illegal outposts.
Zohar Sabah
Runs a settler outpost named Zohar’s Farm and has previously faced charges of violence against Palestinians. He was indicted by Israel’s State Attorney’s Office in September for allegedly participating in a violent attack against Palestinians and activists in the West Bank village of Muarrajat.
Coco’s Farm and Neria’s Farm
These are illegal outposts in the West Bank, which are at the vanguard of the settler movement. According to the UK, they are associated with people who have been involved in enabling, inciting, promoting or providing support for activities that amount to “serious abuse”.
Dengue%20fever%20symptoms
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Benefits of first-time home buyers' scheme
- Priority access to new homes from participating developers
- Discounts on sales price of off-plan units
- Flexible payment plans from developers
- Mortgages with better interest rates, faster approval times and reduced fees
- DLD registration fee can be paid through banks or credit cards at zero interest rates
Jetour T1 specs
Engine: 2-litre turbocharged
Power: 254hp
Torque: 390Nm
Price: From Dh126,000
Available: Now
The specs
- Engine: 3.9-litre twin-turbo V8
- Power: 640hp
- Torque: 760nm
- On sale: 2026
- Price: Not announced yet
MATCH INFO
Watford 1 (Deulofeu 80' p)
Chelsea 2 (Abraham 5', Pulisic 55')
COMPANY%20PROFILE
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