How quickly does COVID immunity fade? What scientists know

Cassandra Willyard

Nature | February 02, 2023

A kiosk in Shanghai, China, offers free SARS-CoV-2 testing.Credit: CFOTO/Future Publishing via Getty

Three years into the pandemic, the immune systems of the vast majority of humans have learnt to recognize SARS-CoV-2 through vaccination, infection or, in many cases, both. But just how quickly do these types of immunity fade?

New evidence suggests that ‘hybrid’ immunity, the result of both vaccination and a bout of COVID-19, can provide partial protection against reinfection for at least eight months¹. It also offers greater than 95% protection against severe disease or hospitalization for between six months and a year after an infection or vaccination, according to estimates from a meta-analysis². Immunity acquired by booster vaccination alone seems to fade somewhat faster.

China and India approve nasal COVID vaccines — are they a game changer?

Scientists hope the immunizations, delivered through the nose or mouth, will prevent even mild cases of illness.

Emily Waltz

Nature | September 06, 2022

CanSino Biologics’ inhaled vaccine has the same ingredients as the company’s COVID-19 shot that is already available in China.Credit: Chen Yuancai/VCG/Getty

Two needle-free COVID-19 vaccines that are delivered through the nose or mouth have been approved for use in China and India. China’s new vaccine, announced on Sunday, is inhaled through the nose and mouth as an aerosolized mist, and India’s, announced on Tuesday, is administered as drops in the nose.

These mucosal vaccines target thin mucous membranes that line the nose, mouth and lungs. By prompting immune responses where SARS-CoV-2 first enters the body, mucosal vaccines could, in theory, prevent even mild cases of illness and block transmission to other people — something COVID-19 shots have been unable to do. Vaccines that produce sterilizing immunity would be game changing for the pandemic.

How nasal-spray vaccines could change the pandemic

Vaccines inhaled through the mouth or nose might stop the coronavirus in its tracks, although there’s little evidence from human trials so far.

Emily Waltz

Nature | September 06, 2022

A student in Washington DC receives an influenza nasal-spray vaccine, in 2009. Intranasal and oral COVID-19 vaccines are now in development. Credit: Hyungwon Kang/Reuters

Editor’s note: Indian regulators approved Bharat Biotech’s intranasal vaccine for emergency use on 6 September.

Are sprays the future of COVID-19 vaccines?

That’s the hope of dozens of research groups and companies working on new kinds of inoculation. Rather than relying on injections, these use sprays or drops administered through the nose or mouth that aim to improve protection against the virus SARS-CoV-2.

COVID vaccines slash risk of spreading Omicron — and so does prior infection

But the benefit of vaccines in reducing Omicron transmission doesn’t last for long.

Ruby Prosser Scully

Nature | August 26, 2022

Vaccinated people are less likely to pass on Omicron than those who have not been immunized.Credit: Frederic J. Brown/AFP/Getty

People who become infected with the Omicron variant are less likely to spread the virus to others if they have been vaccinated or have had a prior SARS-CoV-2 infection, according to a study in US prisons¹. And people who have had a prior infection and been vaccinated are even less likely to pass on the virus, although the benefit of vaccines in reducing infectiousness seems to wane over time.

The findings are good news, says Megan Steain, a virologist at the University of Sydney, Australia. They show that the more exposure people have to the virus, whether through vaccines, boosters or infections, the “higher the wall of immunity”, she says. “If we can keep high levels of booster vaccinations up, then we can decrease how infectious people are when they’re sick,” says Steain.

The study was posted as a preprint on medRxiv this month and has not been peer reviewed.

China approves first homegrown COVID antiviral

The country’s drug regulator has granted conditional authorization for an HIV drug to be used to treat COVID-19.

Yvaine Ye

Nature | July 26, 2022

A temporary hospital for people with COVID-19 in Shanghai. The country has approved the first antiviral for the disease made in China. Credit: Ray Young/Feature China/Future Publishing/Getty

China’s drug regulator granted conditional approval on Monday for an HIV drug to be used to treat COVID-19. The drug, Azvudine, developed by Chinese drugmaker Genuine Biotech, is the first oral antiviral for the disease made in China.

Genuine Biotech, headquartered in Pingdingshan, applied for regulatory approval earlier this month. In an announcement, the company said that 40% of people with COVID-19 who were given Azvudine for a week in a phase III clinical trial showed “improved clinical symptoms”, compared with 11% of those given a placebo. However, detailed data from the trial, including whether the treatment reduced the risk of hospitalization or death, have not been released.

How different COVID-19 recovery paths affect human health, environmental sustainability, and food affordability: a modelling study

Juliette Maire, PhD; Aimen Sattar, MPhil; Roslyn Henry, PhD; Frances Warren, PhD; Magnus Merkle, MSc; Prof Mark Rounsevell, PhD; and Peter Alexander, PhD

The Lancet | Open Access | Published: July, 2022 | DOI: https://doi.org/10.1016/S2542-5196(22)00144-9

Summary
Background
The COVID-19 pandemic arrived at a time of faltering global poverty reduction and increasing levels of diet-related diseases, both of which have a strong link to poor outcomes for those with COVID-19. Governments responded to the pandemic by placing unprecedented restrictions on internal and external movements, which have resulted in an economic contraction. In response to the economic shock, G20 governments have committed to providing US$14 trillion stimuli to support economic recovery. We aimed to assess the impact of different COVID-19 recovery paths on human health, environmental sustainability, and food sustainability.

How months-long COVID infections could seed dangerous new variants

Tracking SARS-CoV-2 evolution during persistent cases provides insight into the origins of Omicron and other global variants. What can scientists do with this knowledge?

Ewen Callaway

Nature | June 15, 2022

These are mutations that accumulated in the spike protein of SARS-CoV-2 during a seven-month-long infection.Illustration by Nik Spencer/Nature; Source: Ref. 1

Virologist Sissy Sonnleitner tracks nearly every COVID-19 case in Austria’s rugged eastern Tyrol region. So, when one woman there kept testing positive for months on end, Sonnleitner was determined to work out what was going on.

Before becoming infected with SARS-CoV-2 in late 2020, the woman, who was in her 60s, had been taking immune-suppressing drugs to treat a lymphoma relapse. The COVID-19 infection lingered for more than seven months, causing relatively mild symptoms, including fatigue and a cough.

Sonnleitner, who is based at a microbiology facility in Außervillgraten, Austria, and her colleagues collected more than two dozen viral samples from the woman over time and found through genetic sequencing that it had picked up about 22 mutations (see ‘Tracking spike’s evolution’). Roughly half of them would be seen again in the heavily mutated Omicron variants of SARS-CoV-2 that surged around the globe months later¹. “When Omicron was found, we had a great moment of surprise,” Sonnleitner says. “We already had those mutations in our variant.”

Most US kids have caught the coronavirus, antibody survey finds

Study shows that infections in very young children doubled during the Omicron wave.

Smriti Mallapaty

Nature | May 05, 2022

Credit: Sarah Silbiger/UPI/Shutterstock

Roughly two in every three children aged between one and four years old in the United States have been infected with SARS-CoV-2, according to a nationwide analysis¹. Infections in that age group increased more than in any other during the Omicron wave, which researchers say demonstrates the variant’s high transmissibility.

Researchers looked for COVID-19 antibodies in blood samples from more than 86,000 children under 18 years old — including some 6,100 children aged between one and four. In the youngest children, the number of infections more than doubled, from 33% to 68% between December 2021 and February 2022.

Since vaccination of children was completed, no Cuban boy or girl has died

Granma | January 26, 2022

More than 1.6 million children have been vaccinated against COVID-19 in Cuba, and since the conclusion of the campaign, no pediatric deaths have been reported

India: COVID-19 third wave: How do Delhi’s hospitals fare?

DTE visited a few hospitals in the national capital to take a pulse of the situation

Taran Deol

Down To Earth | January 06, 2022

The third wave of the COVID-19 pandemic in India sparked by the new variant of concern omicron has stoked fears about an unprecedented rise in cases, followed by a rise in hospitalisations and an overburdened healthcare system — as was seen in the ghastly second wave of April 2021.

India’s metropolitan cities are the epicentre of the third wave of COVID-19 cases. With 2,135 infections of the new variant across the country as of January 5, 2022 — 653 in Maharashtra and 464 in Delhi alone — omicron is fast establishing its dominance.

With 11,665 new cases in the last 24 hours, dedicated COVID-19 hospitals in the national capital are preparing for an unprecedented rise in cases, even though evidence, for now, suggests that omicron infections remain mostly mild.

Down to Earth visited a few hospitals in the national capital to take a pulse of the situation.