How the ageing immune system makes older people vulnerable to Covid-19

‘Covid-19 patients who are 80 or older are hundreds of times more likely to die than those under 40. That’s partly because they are more likely to have underlying conditions — like diabetes and lung disease — that seem to make the body more vulnerable to Covid-19.

‘But some scientists suggest another likely, if underappreciated, driver of this increased risk: the ageing immune system. The changes that ripple through our network of immune cells as the decades pass are complex, resulting in an overreaction here, a delayed response there and, overall, a strangely altered landscape of immunity.’

Read here (Today Online, Sept 13, 2020) 

Face masks could be giving people Covid-19 immunity, researchers suggest

‘Face masks may be inadvertently giving people Covid-19 immunity and making them get less sick from the virus, academics have suggested in one of the most respected medical journals in the world.  The commentary, published in the New England Journal of Medicine, advances the unproven but promising theory that universal face mask wearing might be helping to reduce the severity of the virus and ensuring that a greater proportion of new infections are asymptomatic. 

‘If this hypothesis is borne out, the academics argue, then universal mask-wearing could become a form of variolation (inoculation) that would generate immunity and “thereby slow the spread of the virus in the United States and elsewhere” as the world awaits a vaccine. It comes as increasing evidence suggests that the amount of virus someone is exposed to at the start of infection - the “infectious dose” - may determine the severity of their illness. Indeed, a large study published in the Lancet last month found that “viral load at diagnosis” was an “independent predictor of mortality” in hospital patients.’

Read here (The Telegraph, Sept 12, 2020) 

Iceland has very good news about coronavirus immunity

‘A study on the pandemic in Iceland published in the New England Journal of Medicine offers some evidence to dispel such fears. The researchers have looked at serum samples from 30,576 individuals, using six different types of antibody testing (since different techniques often produce conflicting results).

‘The paper’s central findings are that, out of 1,797 tested people who’d recovered from Covid, 91.1% produced detectable levels of antibodies. Moreover, these levels hadn’t declined four months after the diagnosis. The immune response was higher among older individuals — who are at greater risk of developing a more dangerous form of the coronavirus — and among those who presented the worst symptoms.’

Read here (Bloomberg, Sept 3, 2020)

Sex differences in COVID-19 immune responses affect patient outcomes

‘Yale researchers have identified significant differences in how the immune systems of women and men respond to the virus that causes COVID-19. In a study launched by Women’s Health Research at Yale and published Aug. 28 in Nature, the authors revealed possible biological explanations for why men are more likely than women to suffer severe cases of COVID-19 and die of the disease.

“We now have clear data suggesting that the immune landscape in COVID-19 patients is considerably different between the sexes and that these differences may underlie heightened disease susceptibility in men,” said senior author Akiko Iwasaki, the Waldemar Von Zedtwitz Professor of Immunobiology and Molecular, Cellar and Development Biology, and an investigator of the Howard Hughes Medical Institute. “Collectively, these data suggest we need different strategies to ensure that treatments and vaccines are equally effective for both women and men.”

Read here (Yale News, August 26, 2020)

First Covid-19 reinfection documented in Hong Kong, researchers say

‘Researchers in Hong Kong on Monday reported what appears to be the first confirmed case of Covid-19 reinfection, a 33-year-old man who was first infected by SARS-CoV-2 in late March and then, four and a half months later, seemingly contracted the virus again while traveling in Europe.

‘The case raises questions about the durability of immune protection from the coronavirus. But it was also met with caution by other scientists, who questioned the extent to which the case pointed to broader concerns about reinfection...

‘During his second infection, the man did not have any symptoms. Some patients go through their course of Covid-19 without showing symptoms, but researchers have also hypothesized that secondary cases of the coronavirus will generally be milder than the first.’

Read here (STAT News, August 24, 2020)

China drug regulator says Covid-19 vaccines must have 50 percent efficacy rate to be approved for use

‘China's drug regulator has said COVID-19 vaccine candidates must have a 50 percent efficacy rate and be able to provide users with at least six moths' immunity from the virus if they are to be approved in the country. A draft document released by the Chinese Centre for Drug Evaluation (CCDE) laid out the guidelines, stipulating that while 50 percent efficacy is the minimum, the target is that vaccines should be effective for 70 percent of the population.’

Read here (Newsweek, August 15, 2020)

The people with hidden immunity against Covid-19

‘While the latest research suggests that antibodies against Covid-19 could be lost in just three months, a new hope has appeared on the horizon: the enigmatic T cell... T cells are a kind of immune cell, whose main purpose is to identify and kill invading pathogens or infected cells. It does this using proteins on its surface, which can bind to proteins on the surface of these imposters... Several studies have shown that people infected with Covid-19 tend to have T cells that can target the virus, regardless of whether they have experienced symptoms...

‘Most bizarrely of all, when researchers tested blood samples taken years before the pandemic started, they found T cells which were specifically tailored to detect proteins on the surface of Covid-19. This suggests that some people already had a pre-existing degree of resistance against the virus before it ever infected a human. And it appears to be surprisingly prevalent: 40-60% of unexposed individuals had these cells.’

Read here (BBC, July 20, 2020)

Swiftly waning Covid-19 immunity poses vaccination challenge

‘Emerging evidence that the body's immune defence against Covid-19 may be short-lived makes it even harder for vaccine developers to come up with shots fully able to protect people in future waves of infection, scientists said on Tuesday.

‘Preliminary studies in China, Germany, Britain and elsewhere have found that patients infected with the novel coronavirus make protective antibodies as part of their immune system's defences, but these appear to last only a few months.’

Read here (Malaysiakini, July 15, 2020)

Antibody levels in recovered COVID-19 patients decline quickly, Chinese study finds

‘Levels of an antibody found in recovered COVID-19 patients fell sharply in two to three months after infection for both symptomatic and asymptomatic patients, according to a Chinese study, raising questions about the length of any immunity against the novel coronavirus. The research, published in Nature Medicine on Jun 18, highlights the risks of using COVID-19 "immunity passports" and supports the prolonged use of public health interventions such as social distancing and isolating high-risk groups, researchers said.’

Read here (Channel News Asia, June 22, 2020)

Antibody tests don't mean a ton right now. But that could change soon

‘In the study published in medRxiv, a preprint server for posting studies before they are peer-reviewed, a team at the Lindsley F. Kimball Research Institute of the New York Blood Center and Rockefeller University analyzed 370 plasma samples donated from people who recovered from COVID-19 and found some surprising results...

‘Overall, around 88% of the people generated varying levels of antibodies to the virus. But only about 10% of them had high levels that were able to neutralize the lab-based version of the COVID-19 virus—and, on the other side of the spectrum, 17% had almost no antibody response to their infection.’

Read here (Time Magazine, June 16, 2020)

Immunity to the coronavirus remains a mystery. Scientists are trying to crack the case

‘With Covid-19, immunity — whether from an infection or a vaccine — is expected to wane over perhaps a few years; that is what happens with the four human coronaviruses that cause colds. If that pattern extends to this virus, people will gradually become more susceptible to the virus after some amount of time (though they may be less likely to get a severe case). Tracking the levels of the different correlates could provide clues to how long immunity lasts, and when a person becomes vulnerable again. It could also indicate when people might need another dose of the vaccine.’

Read here (STAT News, June 11, 2020)

‘Are you immune?’ The new class system that could shape the Covid-19 world

‘...experts predict that if survivors are found to be immune, they could perform a range of jobs and services – such as volunteering in hospitals and nursing homes, caring for coronavirus patients and working in shops and food processing plants – risk-free. And, depending on how authorities, business and society at large respond, they could also be entitled to greater freedoms.’

Read here (The Guardian, June 10, 2020)

Are we underestimating how many people are resistant to Covid-19?

‘One thing seems clear: there are many reasons why one population is more protected than another. Theoretical epidemiologist Sunetra Gupta of the University of Oxford thinks that a key one is immunity that was built up prior to this pandemic. “It’s been my hunch for a very long time that there is a lot of cross-protection from severe disease and death conferred by other circulating, related bugs,” she says...

‘Socioeconomic status, climate, culture and genetic makeup could also shape vulnerability, as could certain childhood vaccines and vitamin D levels. And all of these factors can vary between countries.’

Read here (The Guardian, June 7, 2020)

Covid-19 patients no longer infectious 11 days after getting sick, research shows

‘After 11 days of getting sick, Covid-19 patients no longer pose a risk of spreading the disease - which means they can be safely discharged. Singapore now discharges patients only after two swab tests are negative for the virus. But a local study has shown that while the patients might test positive, it "does not equate to infectiousness or viable virus". That's because the test detects parts of the virus' genome, but is unable to show if they are just fragments of the virus, or if an intact virus is no longer viable and can't infect anyone.’

Read here (Straits Times, May 23, 2020)

The world needs Covid-19 vaccines. It may also be overestimating their power

‘In the public imagination, vaccines are often seen effectively as cure-alls, like inoculations against measles. Rather than those vaccines, however, the Covid-19 vaccines in development may be more like those that protect against influenza — reducing the risk of contracting the disease, and of experiencing severe symptoms should infection occur, a number of experts told STAT.’

Read here (STAT News, May 22, 2020)

First human trial of COVID-19 vaccine finds it is safe and induces rapid immune response

‘These results represent an important milestone. The trial demonstrates that a single dose of the new adenovirus type 5 vectored COVID-19 (Ad5-nCoV) vaccine produces virus-specific antibodies and T cells in 14 days, making it a potential candidate for further investigation,’ says Professor Wei Chen from the Beijing Institute of Biotechnology in Beijing, China, who is responsible for the study. ‘However, these results should be interpreted cautiously. The challenges in the development of a COVD-19 vaccine are unprecedented, and the ability to trigger these immune responses does not necessarily indicate that the vaccine will protect humans from COVID-19. This result shows a promising vision for the development of COVID-19 vaccines, but we are still a long way from this vaccine being available to all.’

Read here (Science Daily, May 22, 2020)

This is the original report in The Lancet. Read here (The Lancet, May 22, 2020)

Why we might not get a coronavirus vaccine

‘When the prime minister, Boris Johnson, told a No 10 press briefing that a vaccine was “by no means guaranteed”, his chief scientific adviser, Patrick Vallance, agreed, but added: “I’d be surprised if we didn’t end up with something.” Many scientists share that view... In all likelihood, a coronavirus vaccine will not be 100% effective.’

Read here (The Guardian, May 22, 2020)

South Korea says patients who re-tested positive after recovering were no longer infectious

‘Survivors of Covid-19 who re-tested positive for the disease after making a full recovery were no longer infectious or a risk to their loved ones, South Korea's health agency announced Monday, adding a new clue to the ongoing mysteries surrounding Covid-19 immunity.’

Read here (Forbes, May 18, 2020)

Study shows most people carry antibodies after recovery from coronavirus

‘A new study offers a glimmer of hope in the grim fight against the coronavirus: Nearly everyone who has had the disease - regardless of age, sex or severity of illness - makes antibodies to the virus. The study, posted online on Tuesday (May 5) but not yet reviewed by experts, also hints that anyone who has recovered from infection may safely return to work - although it is unclear how long their protection might last.’

Read here (Straits Times, May 8, 2020)

What Covid-19 antibody tests can and cannot tell us

‘Dozens of antibody tests for the novel coronavirus have become available in recent weeks. And early results from studies of such serological assays in the U.S. and around the world have swept headlines. Despite optimism about these tests possibly becoming the key to a return to normal life, experts say the reality is complicated and depends on how results are used.

‘Antibody tests could help scientists understand the extent of COVID-19’s spread in populations. Because of limitations in testing accuracy and a plethora of unknowns about immunity itself, however, they are less informative about an individual’s past exposure or protection against future infection.’

Read here (Scientific American, May 5, 2020)