Pfizer vaccine does not affect sperm, reveals study

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.

Pfizer vaccine appears not to affect sperm

The Covid-19 mRNA vaccine from Pfizer 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 months after the men were vaccinated. None of their sperm parameters - volume, concentration, or motility - had changed significantly after vaccination, the researchers reported Monday on medRxiv ahead of peer review.

Technology behind Pfizer's Covid-19 vaccine can be used to fight cancer

"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 Covid-19 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% reported sleep problems, 24.4% had fatigue, 20.2% scored poorly on objective tests of cognition, 19.1% reported anxiety, and 15.7% 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% 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 hospitalization 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.

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.

Pfizer vaccine effective in those with chronic illnesses

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% to 50% 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.

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 co-author 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.