A large UK study finds that a vaccinated person, who nevertheless becomes infected with the coronavirus, has a much lower risk of transmitting the virus to household members.
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, the illness caused by the virus.
Vaccines protect unvaccinated household members, too
Compared to an unvaccinated Covid-19 patient, a vaccinated person who nevertheless becomes infected with the coronavirus has a much lower risk of transmitting the virus to household members, a large UK study found.
Researchers at Public Health England studied more than 365,000 households with a first Covid-19 infection, including more than 24,000 households in which the so called "index case" of Covid-19 was someone who had received at least one dose of either the Pfizer/BioNTech vaccine or the Oxford-AstraZeneca vaccine.
When the first dose had been given at least 21 days previously - as was the case in 4,107 of the households studied - the risk of virus transmission from vaccinated individuals to their household members was 40 percent to 50 percent lower than the risk of transmission from Covid-19 patients who had not been vaccinated, the researchers found.
The effects were similar for both the Pfizer and AstraZeneca vaccines and started to become evident around 14 days after the first dose, according to a report posted ahead of peer review on Knowledge Hub.
Along with the vaccines' success at preventing infections and reducing the severity of infections that do occur, the new findings show they are "associated with reduced likelihood of household transmission ... highlighting important wider benefits to close contacts," the authors conclude.
Pfizer/BioNTech vaccine appears not to affect sperm
The Covid-19 mRNA vaccine from Pfizer Inc and BioNTech SE does not damage sperm, according to a study by Israeli researchers.
They collected sperm samples from 43 male volunteers before and roughly a month after the men were vaccinated. None of their sperm parameters - volume, concentration, or motility - had changed significantly after vaccination, the researchers reported on medRxiv ahead of peer review.
"These preliminary results are reassuring to the young male population undergoing vaccination worldwide," the researchers said.
"Couples desiring to conceive should vaccinate, as vaccination does not affect sperm," whereas previous studies have shown that coronavirus infection does affect sperm adversely.
Neuropsychiatric symptoms persist in virus survivors
Neuropsychiatric symptoms are common in Covid-19 survivors, a large new analysis confirms. Researchers pooled data from 51 studies involving a total of nearly 19,000 patients who were tracked for up to six months.
The average follow-up was 77 days post-diagnosis. Overall, 27.4 percent reported sleep problems, 24.4 percent had fatigue, 20.2 percent scored poorly on objective tests of cognition, 19.1 percent reported anxiety, and 15.7 percent had post-traumatic stress.
Nerve disturbances and dizziness or vertigo were less common but were seen in "a non-negligible proportion" of patients, the research team reported on Tuesday in a paper posted on medRxiv ahead of peer review.
Only about 7 percent of the patients were said to have required intensive care, based on this meta-analysis in which some papers were not clear on intensive care figures.
"There was little or no evidence of differential symptom prevalence based on hospitalisation status, severity, or follow-up duration," the researchers said.
They caution that some of the patients may still have been in the acute phase of their infections, and longer follow-up will be necessary to know how long these problems persist, and whether they are effects of viral infection in general or are specific to the new coronavirus.
Covid-19 nasal swab test complications extremely rare
Severe complications associated with nasal swab tests for Covid-19 are very rare, a new study found. Researchers in Finland looked at six months of hospital emergency department data in a region where more than 640,000 such tests had been performed.
They found that only eight patients needed emergency care for swab test-related problems. Four of the eight cases were due to broken swabs and four to uncontrollable nosebleeds.
All of the complications occurred immediately after swab tests, according to a report published on Thursday in JAMA Otolaryngology-Head & Neck Surgery. The overall rate was 1.24 emergencies for every 100,000 performed tests.
While the study may have missed minor complications, it showed that Covid-19 nasopharyngeal swab testing "is safe and complications are extremely rare," said coauthor Dr. Anni Koskinen of the University of Helsinki.
All of the complications seemed to involve an incorrect sampling technique or misdirection of the swab, her team reported. "Force should never be used, especially in patients with known prior operations of the nose or skull base," they advised.