July 26 - The following is a roundup of some of the latest scientific studies on the novel coronavirus and efforts to find treatments and vaccines for Covid-19.
Most people with allergic reactions to the first dose of an mRNA Covid-19 vaccine from either Pfizer/BioNTech or Moderna can safely receive the second dose, a new study shows.
The rates of allergic reactions to these vaccines have been reported to be as high as two per cent, with anaphylaxis, the most serious kind, occurring in up to 2.5 of every 10,000 vaccine recipients, the researchers said.
They reviewed data on 189 adults with first-dose reactions to one of these vaccines, such as flushing, dizziness or lightheadedness, tingling, throat tightness, hives, and wheezing or shortness of breath.
Most of these adults - 84 per cent - received the second dose of the vaccine, with about a third taking an antihistamine beforehand. All of them tolerated the second dose, including those with first-dose anaphylactic reactions.
Any potentially allergic symptoms that developed after the second dose were mild and easily controlled, the researchers reported on Monday (July 26) in JAMA Internal Medicine.
"Complete two-dose vaccination has become even more important with the Delta variant and we suspect there are many more people who did not get their second shot because of allergic symptoms," said co-author Dr. Matthew Krantz from Vanderbilt University.
"Our data suggest that most patients with immediate and potentially allergic reactions to mRNA Covid-19 vaccines tolerate a second dose," his team concluded.
Chinese researchers tracking a recent Covid-19 outbreak in China found that people infected with the Delta variant carry 1,260 times more virus in their noses compared to those infected in the first wave of the pandemic.
The higher load means the virus spreads far more easily from person to person, increasing infections and hospitalizations, they reported ahead of peer review in a paper first posted on medRxiv earlier in July and updated on Friday (July 23).
The interval between when people were exposed to infected individuals and when they themselves were diagnosed decreased from an average of six days in 2020 to four days during the Delta outbreak, the researchers found.
The Delta variant is "outcompeting all other viruses because it just spreads so much more efficiently," said Shane Crotty of the La Jolla Institute for Immunology in San Diego, who was not involved in the Chinese study.
In the United States, Delta accounts for about 83 per cent of new infections, with unvaccinated people representing nearly 97 per cent of severe cases.
Widely-used antacid medications known as proton pump inhibitors (PPIs) are not linked with severe Covid-19 outcomes, a new study found.
Researchers with the US Veterans Affairs Health Care System analyzed data on nearly 15,000 veterans with positive Covid-19 tests, about 42 per cent of whom were using PPIs such as Procter & Gamble's Prilosec (omeprazole), Takeda Pharmaceuticals' Prevacid (lansoprazole), and AstraZeneca's Nexium (esomeprazole).
After taking patients' underlying Covid-19 risk factors into account, the risk of becoming sick enough to need mechanical ventilation or to die within two months of diagnosis was no different between regular PPI users and non-users, the researchers reported on Sunday on medRxiv ahead of peer review.
"With respect to Covid-19," the researchers concluded, "patients and providers should feel safe to continue to use PPIs at the lowest effective dose for approved indications."
