In this week's roundup, the latest scientific research on the coronavirus and efforts to find treatments and vaccines suggest that although COVID-19 is generally milder in vaccinated patients, they can still suffer severe symptoms. Also, antibodies in people who had COVID-19 may not protect them against variants, masks and social distancing are still considered worthwhile and 100 million people have had long haul COVID-19 around the world.
Experimental chewing gum reduces virus load in saliva
Researchers believe that an experimental chewing gum containing a protein that "traps" coronavirus particles could limit the amount of virus in saliva and help curb transmission when infected people are talking, breathing or coughing. The gum contains copies of the Angiotensin-Converting Enzyme 2 (ACE2) protein found on cell surfaces, which the virus uses as a gateway to break into cells and infect them.
In test-tube experiments using saliva and swab samples from infected individuals, virus particles attached themselves to the ACE2 "receptors" in the chewing gum. As a result, the viral load in the samples fell by more than 95%, the research team from the University of Pennsylvania reported in Molecular Therapy.
The gum feels and tastes like conventional chewing gum, can be stored for years at normal temperatures, and chewing it does not damage the ACE2 protein molecules, the researchers said. Using gum to reduce viral loads in saliva, they suggest, would add to the benefit of vaccines and would be particularly useful in countries where vaccines are not yet available or affordable.
Protection may last longer after the vaccine booster dose
Protection against the COVID-19 from a messenger RNA (mRNA) vaccine – either the Moderna or Pfizer/BioNTech shots – may last longer after the booster dose than after the original two-shot regimen, researchers speculated based on the results of a small new study. They measured vaccine responses before and after the boosters in 33 healthy middle-aged adults who had received their second doses an average of nine months earlier.
Before the boosters, their antibody levels had decreased about 10 times from levels early after their second dose. By six to 10 days after the booster, their antibody levels had climbed 25 times and were five times higher than after two doses of the vaccine, according to a report posted on Sunday on medRxiv ahead of peer review.
Among the volunteers who had COVID-19 before being vaccinated, antibody levels after the booster were 50 times higher than after their infections. "Because these antibody levels are so robust, the booster could potentially give us protection for a longer duration than what we saw for two doses of the vaccine," study coauthor Alexis Demonbreun of Northwestern University Feinberg School of Medicine in Chicago said in a statement.
Blood test detects virus exposure without antibodies
Because not everyone produces measurable amounts of COVID-19 antibodies after infection or vaccination, U.K. researchers have developed a single blood test that not only detects antibodies but also measures other signs of an immune system response to the virus. Precisely, it measures T cells, powerful immune cells that learn to recognize the virus either after encountering it during infection or through vaccination.
As part of the new test, blood samples are exposed to replicas of small pieces of the virus. If the T cells in the blood sample recognize these pieces, they are triggered to produce molecules that can be easily measured, such as the inflammatory protein interferon-gamma.
"The test is very sensitive and seems to be accurate," said Martin Scurr of Cardiff University School of Medicine, coauthor of a report published on Immunology. This was true even in patients with cancer, many of whom do not produce antibodies in response to vaccination.
"The test is easy to employ and should play a very useful role" in monitoring antibody and T cell responses to the virus, Scurr said. "However, it remains to be determined what level of antibody and the T cell response against the virus might protect from future infection and the COVID-19."
Long COVID risk not lower after breakthrough infection
COVID-19 vaccines are highly effective in protecting against serious illness, but they do not protect against "long COVID" in people who become infected despite vaccination, new data show.
For six months, researchers tracked 9,479 vaccinated individuals diagnosed with COVID-19 and about the same number of infected unvaccinated patients. Compared to the unvaccinated patients, people with so-called breakthrough infections were "at a much lower risk of severe complications of COVID-19," such as the need to be admitted to an intensive care unit (ICU), requiring breathing assistance or developing a blood clot in their legs or lungs, said Maxime Taquet of the University of Oxford. But other complications of the virus, including the syndrome of lingering symptoms known as long COVID, occurred at similar rates regardless of vaccination status, his team said in a paper posted on medRxiv ahead of peer review.
In people over the age of 60 with breakthrough infections, vaccines protected against COVID-19 complications only weakly or not at all, Taquet noted. "Vaccines are still an excellent way to prevent any complication of COVID-19 (including long COVID) since they prevent infection in the first place," Taquet said. "However, these findings show that those who get infected despite being vaccinated should remain vigilant about potential complications of their illness."
COVID-19 survival has improved for European cancer patients
European cancer patients infected with COVID-19 are much more likely to survive now than they were earlier in the pandemic, researchers found. They reviewed the outcomes of more than 2,600 cancer patients with coronavirus infections treated in six countries between February 2020 and February 2021 to calculate death rates within the first two weeks after diagnosis.
"The initial studies on the topic documented a mortality rate ranging from 30% to 40% ... in patients with cancer," said Dr. David James Pinato of Imperial College London. "Our study suggests that over the course of the pandemic, the mortality has gradually reduced, even before vaccines were implemented, reducing to a figure that was as low as 12.5% during the so-called 'second wave' in Europe."
Cancer patients diagnosed earlier in the pandemic also had more COVID-19 complications, his team reported on Wednesday in JAMA Oncology. The researchers believe the improved survival is related not only to better treatments but also to the better availability of COVID-19 tests that allow for earlier diagnosis. These factors "have been key in improving overall outcome," Pinato said.
'Glimpse of hope' when drugs limit vaccine antibodies
People taking a class of drugs known to limit the antibody response of the mRNA COVID-19 vaccines from Pfizer /BioNTech or Moderna may get some protection from another part of the immune system, according to a small study published on Clinical Infectious Diseases.
The class of anti-CD20 drugs used to treat rheumatoid arthritis, some cancers and other conditions such as Roche's Rituxan (rituximab), suppress the immune system. But the new findings offer "a glimpse of hope" that these patients may get some protection from the mRNA vaccines, after all, the study's leader said.
The researchers studied mRNA vaccine responses in 37 patients taking these drugs for rheumatic diseases or multiple sclerosis, comparing them to 22 individuals with healthy immune systems. Only about 70% of the patients developed antibodies in response to the mRNA vaccines, and their levels were significantly lower than levels in the healthy volunteers. However, both groups had equal levels of immune cells called the T cells that could recognize and attack the coronavirus.
"Our study suggests that patients on anti-CD20 treatment are able to mount potent the T-cell responses to mRNA COVID-19 vaccines," despite impaired antibody responses, the researchers wrote. The size of the study "does not allow us to draw firm conclusions about protection from severe COVID-19 in these patients," said Dr. Christiane Eberhardt of the University of Geneva in Switzerland. They "should still be vigilant and protect themselves from getting infected."