Saudi Press

Saudi Arabia and the world
Wednesday, Sep 17, 2025

The Delta variant spreads regardless of people's vaccination status, a new U.K. study shows

The Delta variant spreads regardless of people's vaccination status, a new U.K. study shows

In a yearlong study of 621 people with COVID-19, scientists found that their peak viral load was similar regardless of vaccination status.
People inoculated against COVID-19 are just as likely to spread the Delta variant of the virus to contacts in their household as those who haven’t had shots, according to new research.

In a yearlong study of 621 people in the U.K. with mild COVID-19, scientists found that their peak viral load was similar regardless of vaccination status, according to a paper published Thursday in The Lancet Infectious Diseases medical journal. The analysis also found that 25% of vaccinated household contacts still contracted the disease from an index case, while 38% of those who hadn’t had shots became infected.

The results go some way toward explaining why the Delta variant is so infectious even in nations with successful vaccine rollouts, and why the unvaccinated can’t assume they are protected because others have had shots. Those who were inoculated cleared the virus more quickly and had milder cases, while unvaccinated household members were more likely to suffer from severe disease and hospitalization.

“Our findings show that vaccination alone is not enough to prevent people from being infected with the Delta variant and spreading it in household settings,” said Ajit Lalvani, a professor of infectious diseases at Imperial College London who co-led the study. “The ongoing transmission we are seeing between vaccinated people makes it essential for unvaccinated people to get vaccinated to protect themselves.”

Vaccination was found to reduce household transmission of the alpha variant—first discovered in the U.K. in late 2020—by between 40% and 50%, and infected vaccinated individuals had a lower viral load in the upper respiratory tract than those who hadn’t had shots. The Delta variant has been the dominant strain globally for some time, however.

The research also showed that immunity from full vaccination waned in as little as three months. The authors said there wasn’t enough data to advise on whether this should lead to a change in the U.K.’s booster policy, where third doses are currently being offered to older and more vulnerable people six months after their second shot.

Six months was an arbitrary time period chosen following early data from Israel on the effectiveness of boosters, but there is no reason to believe they would be less effective if given earlier, said Neil Ferguson, an epidemiologist at Imperial College London and investigator on the study, at a press briefing Thursday.

The booster program could help halt the virus, as extra shots or repeated infections tend to lead to longer immunological memory, potentially protecting people for up to a year, Lalvani said. More data are needed to confirm this, he said.

The authors didn’t analyze infections based on the type of vaccines people had received. Maria Zambon, head of influenza and respiratory virology at the U.K. Health Security Agency, noted that there are still more than 300 vaccines in development, and said it’s possible that future generations of shots may be better at preventing transmission.
Newsletter

Related Articles

Saudi Press
0:00
0:00
Close
Sam Altman sells the 'Wedding Estate' in Hawaii for 49 million dollars
Turkish car manufacturer Togg Enters German Market with 5-Star Electric Sedan and SUV to Challenge European EV Brands
World’s Longest Direct Flight China Eastern to Launch 29-Hour Shanghai–Buenos Aires Direct Flight via Auckland in December
New OpenAI Study Finds Majority of ChatGPT Use Is Personal, Not Professional
Kuwait opens bidding for construction of three cities to ease housing crunch.
This Week in AI: Meta’s Superintelligence Push, xAI’s Ten Billion-Dollar Raise, Genesis AI’s Robotics Ambitions, Microsoft Restructuring, Amazon’s Million-Robot Milestone, and Google’s AlphaGenome Update
Indian Student Engineers Propose “Project REBIRTH” to Protect Aircraft from Crashes Using AI, Airbags and Smart Materials
Could AI Nursing Robots Help Healthcare Staffing Shortages?
Turkish authorities seize leading broadcaster amid fraud and tax investigation
Qatari prime minister says Netanyahu ‘killed any hope’ for Israeli hostages
Apple Introduces Ultra-Thin iPhone Air, Enhanced 17 Series and New Health-Focused Wearables
Big Oil Slashes Jobs and Investments Amid Prolonged Low Crude Prices
Social Media Access Curtailed in Turkey After CHP Calls for Rallies Following Police Blockade of Istanbul Headquarters
Did the Houthis disrupt the internet in the Middle East? Submarine cables cut in the Red Sea
Gold Could Reach Nearly $5,000 if Fed Independence Is Undermined, Goldman Sachs Warns
Uruguay, Colombia and Paraguay Secure Places at 2026 World Cup
Trump Administration Advances Plans to Rebrand Pentagon as Department of War Instead of the Fake Term Department of Defense
Tether Expands into Gold Sector with Profit-Driven Diversification
Trump’s New War – and the ‘Drug Tyrant’ Fearing Invasion: ‘1,200 Missiles Aimed at Us’
At the Parade in China: Laser Weapons, 'Eagle Strike,' and a Missile Capable of 'Striking Anywhere in the World'
Information Warfare in the Age of AI: How Language Models Become Targets and Tools
Israeli Airstrike in Yemen Kills Houthi Prime Minister
After the Shock of Defeat, Iranians Yearn for Change
YouTube Altered Content by Artificial Intelligence – Without Permission
Iran Faces Escalating Water Crisis as Protests Spread
More Than Half a Million Evacuated as Typhoon Kajiki Heads for Vietnam
HSBC Switzerland Ends Relationships with Over 1,000 Clients from Saudi Arabia, Lebanon, Qatar, and Egypt
Sharia Law Made Legally Binding in Austria Despite Warnings Over 'Incompatible' Values
Dogfights in the Skies: Airbus on Track to Overtake Boeing and Claim Aviation Supremacy
Tim Cook Promises an AI Revolution at Apple: "One of the Most Significant Technologies of Our Generation"
Are AI Data Centres the Infrastructure of the Future or the Next Crisis?
Miles Worth Billions: How Airlines Generate Huge Profits
Zelenskyy Returns to White House Flanked by European Allies as Trump Pressures Land-Swap Deal with Putin
Beijing is moving into gold and other assets, diversifying away from the dollar
Cristiano Ronaldo Makes Surprise Stop at New Hong Kong Museum
Zelenskyy to Visit Washington after Trump–Putin Summit Yields No Agreement
High-Stakes Trump-Putin Summit on Ukraine Underway in Alaska
Iranian Protection Offers Chinese Vehicle Shipments a Cost Advantage over Japanese and Korean Makers
Saudi Arabia accelerates renewables to curb domestic oil use
Cristiano Ronaldo and Georgina Rodríguez announce engagement
Asia-Pacific dominates world’s busiest flight routes, with South Korea’s Jeju–Seoul corridor leading global rankings
Private Welsh island with 19th-century fort listed for sale at over £3 million
Sam Altman challenges Elon Musk with plans for Neuralink rival
Australia to Recognize the State of Palestine at UN Assembly
The Collapse of the Programmer Dream: AI Experts Now the Real High-Earners
Armenia and Azerbaijan to Sign US-Brokered Framework Agreement for Nakhchivan Corridor
British Labour Government Utilizes Counter-Terrorism Tools for Social Media Monitoring Against Legitimate Critics
WhatsApp Deletes 6.8 Million Scam Accounts Amid Rising Global Fraud
Nine people have been hospitalized and dozens of salmonella cases have been reported after an outbreak of infections linked to certain brands of pistachios and pistachio-containing products, according to the Public Health Agency of Canada
Texas Residents Face Water Restrictions While AI Data Centers Consume Millions of Gallons
×