New research out of York University has found the transmission of COVID-19 is much higher in households than in workplaces, schools or the community as the potential for prolonged contact with infected people is greater in the home.

The researchers looked at testing rates and turnaround times, vaccine efficacy, coverage and transmission, waning immunity, and public health measures under various lockdown, reopening and resurgence scenarios—from March to December 2020—to find the best global vaccination strategies to control COVID-19 outbreaks.

They found testing helped mitigate transmission between members of the same household if results were available within the first 24 hours. PCR testing was widely available during this time, which is more sensitive than the current rapid tests, although the researchers believe even this testing is likely to help to curb transmission between family members. Ideally, public health resources would be available for PCR testing.

“Although vaccination helped decrease virus transmission, testing remains an important tool for virus containment as it allows people to isolate sooner,” says York University Professor Huaiping Zhu of York University’s Canadian Center for Disease Modeling in the Faculty of Science and the corresponding author.

The study also looked at what percentage of the population needs to be vaccinated based on the level of immunity to the virus in the community. To control COVID-19 infections when there is waning immunity, 90% of the public needs to be vaccinated. If waning immunity isn’t an issue, only 60% of the population needs to be vaccinated with a vaccine that is at least 70% effective.

Waning immunity could be an issue now heading into winter as recent uptake for booster shots, particularly the bivalent, has been low.

The research team, including lead authors York Postdoctoral Fellows Elena Aruffo and Pei Yuan, found short immunity times coupled with an early relaxation of non-pharmaceutical interventions, such as mask wearing and isolation, are key drivers for disease resurgence.

“High vaccination rates help delay a re-emergence of infection and give public health time to implement new measures. However, even with widespread vaccination, if we are in a high transmission phase of the virus, either most symptomatic people need to be tested or a short testing turnaround time is needed,” says Zhu, director of the NSERC-PHAC “One Health Modeling Network” OMNI.

Vaccine efficacy and distribution, waning immunity and public health measures all play a role in the degree of virus transmission.

“How quickly immunity wanes after vaccination could dictate how the vaccine is best rolled out,” says Zhu. “If immunity lasts a long time, then a fast distribution of vaccine is most beneficial, whereas if the immunity time is short, a slower distribution is more effective as everyone won’t become susceptible at the same time.”

The research team’s model is based on Toronto case data, but can be applied to any region.

The paper, “Community structured model for vaccine strategies to control COVID19 spread: a mathematical study,” is published in the journal PLOS ONE.

York University

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Varicella vaccination resulted in a 99 percent reduction in the incidence of varicella among persons aged younger than 20 years, according to a study presented at the annual meeting of the Infectious Diseases Society of America (IDWeek), held from Oct. 19 to 23 in Washington, D.C.

Mona Marin, M.D., from the U.S. Centers for Disease Control and Prevention in Atlanta, and colleagues analyzed overall and age-specific trends for rates of varicella incidence, hospitalizations, and deaths from the prevaccine period (1990 to 1994) through 2019. Trends were presented for persons aged younger than 50 years, which captures most of the burden of varicella and avoids misclassified herpes zoster in older adults.

The researchers observed dramatic declines in varicella incidence, hospitalization, and mortality rates within 10 years of the one-dose program compared with prevaccine (71 to 90 percent). Limited transmission continued in the school settings, informing change to a two-dose vaccination policy. Declines reached >97, 94, and 97 percent for incidence, hospitalizations, and deaths, respectively, by 2019. Declines were greatest among persons aged younger than 20 years, born during the vaccination program, who had reductions of 99, 97, and >99 percent in incidence, hospitalizations, and deaths, respectively. Further reductions in the number, size, and duration of outbreaks were seen with the two-dose program versus the one-dose program. The proportion of outbreaks with

“This degree of control of the disease in the United States was unimaginable just 25 years ago, but picture that on a global scale,” Marin said in a statement. “As science continues to advance, the chickenpox vaccine is a testament to the transformative power of public health.”

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Experimental Ebola vaccines will be deployed in Uganda in about “two weeks,” a World Health Organization official said Wednesday, as the East African country carried out tough preventive measures that include a lockdown in the Ebola-hit areas.

Potentially hundreds of thousands of trial vaccine doses will buttress a response effort that still must focus on tracing Ebola contacts and community engagement, Dr. Yonas Tegegn Woldemariam, the WHO representative in Uganda, told The Associated Press.

“We are getting closer and closer to deploying vaccines,” he said. “This is a study. This is just another tool that we are going to try.”

Vaccines developed by the U.S.-based Sabin Vaccine Institute and Oxford University “are ready to be shipped” to Uganda, which is finalizing protocols for the study before the National Drug Authority issues import permits, he said.

The Sudan strain of Ebola, for which there’s no proven vaccine, is circulating in Uganda. Ebola, which manifests as a viral hemorrhagic fever, has infected at least 60 people and killed 24. The official figures don’t include people who likely died of Ebola before the outbreak was confirmed. Victims include five health workers.

The Oxford vaccine is being produced by the Serum Institute of India, which has indicated it can eventually make hundreds of thousands of doses available, according to Yonas, who is closely following Uganda’s Ebola response.

Uganda declared an outbreak of Ebola on Sept. 20, several days after the contagious disease began spreading in a rural farming community. A lockdown and nighttime curfew measures are now in place in the outbreak’s epicenter, about 150 kilometers (90 miles) west of the capital, Kampala.

Ebola is spread by contact with bodily fluids of an infected person or contaminated materials. Symptoms include fever, vomiting, diarrhea, muscle pain and at times internal and external bleeding.

Scientists don’t know the natural reservoir of the virus, but they suspect the first victim in an Ebola outbreak gets infected through contact with an infected animal or eating its raw meat. Ugandan officials are still investing the source of the current outbreak.

Uganda has had multiple Ebola outbreaks, including one in 2000 that killed more than 200 people. The 2014-16 Ebola outbreak in West Africa killed more than 11,000 people, the disease’s largest death toll ever.

Ebola was discovered in 1976 in two simultaneous outbreaks in South Sudan and Congo, where it occurred in a village near the Ebola River after which the disease is named.

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