Herd Immunity May Not Be Achievable Even With High Vaccine Uptakehttps://medicalxpress.com/news/2021-01-herd-immunity-high-vaccine-uptake.htmlThe government vaccination program may not be sufficient to achieve herd immunity—even if everyone in the UK is vaccinated—according to new research from the University of East Anglia.
Researchers modeled the effectiveness of UK-wide immunization programs using the Oxford and Pfizer vaccines, taking into account the highly transmissible new COVID-19 variant.They found that the only way to reach herd immunity for the UK would be to vaccinate almost everyone—including children—with the more effective Pfizer vaccine.
They say data for the recently licensed Moderna vaccine would be similar to the Pfizer results.
And the study recommends that all health and social care professionals should receive the 95 percent effective Pfizer/Moderna vaccines to prevent asymptomatic spread to patients and vulnerable people.
... The research team used mathematical models of COVID-19 transmission and vaccine efficacy to predict how well the Oxford and Pfizer vaccines will work to bring the R number down and achieve herd immunity.
Considering the original virus, they initially found that 69 percent of the population would need to be vaccinated with the Pfizer vaccine, or 93 percent of the population with the Oxford vaccine, to bring the R number below 1.0.
However, when they took into account the new more transmissible COVID-19 variant, B.1.1.7,, they found that vaccinating the entire population with the Oxford vaccine would only reduce the R value to 1.325. Meanwhile the Pfizer vaccine would require 82 percent of the population to be vaccinated to control the spread of the new variant.Modeller Prof Alastair Grant, form UEA's School of Environmental Sciences, said:
"The Oxford vaccine reduces the incidence of serious illness to a greater extent than it reduces symptomatic illness, which is still common in those who have had this vaccine."Its efficacy against the incidence of asymptomatic infections is lower, reducing its efficacy against all infection from 70.4 percent to 52.5 percent for the pooled data.
This means that its overall protection against infection is only partial—around 50 percent.
"Although asymptomatic cases are less infectious, including this in our calculations still raises R values by 20 percent or more, from 1.33 to 1.6 for the new variant with a 100 percent vaccination.
"This combination of relatively low headline efficacy and limited effect on asymptomatic infections means that the Oxford vaccine can't take us to herd immunity, even if the whole population is immunized.
"Vaccinating 82 percent of the population with the Pfizer vaccine would control the spread of the virus—but it isn't licensed for use on under 16s, who make up 19 percent of the population.
"Also, some people will refuse the vaccine, so achieving an 82 percent vaccination rate will likely be impossible.
In the absence of vaccination, 'herd immunity' would only occur when 89 percent of the population has had the virus."... "The Oxford vaccine will no doubt be an important control intervention, but unless changes to the dose regime can increase its efficacy, it is unlikely to fully control the virus or take the UK population to herd immunity."
Alastair Grant et al.
Immunisation, asymptomatic infection, herd immunity and the new variants of COVID-19,
Nature (2021)
https://www.medrxiv.org/content/10.1101/2021.01.16.21249946v1 -----------------------------------------------
England's Third Lockdown Sees 'No Evidence of Decline' in Covid Rates, Study Sayshttps://www.cnbc.com/amp/2021/01/21/covid-englands-third-lockdown-sees-no-evidence-of-decline-in-cases.htmlLONDON — A third national lockdown in England appears to have had little impact on the rising rate of coronavirus infections, according to the findings of a major study, with "no evidence of decline" in the prevalence of the virus during the first 10 days of tougher restrictions.
The closely-watched REACT-1 study, led by Imperial College London, warned that health services would remain under "extreme pressure" and the cumulative number of deaths would increase rapidly unless the prevalence of the virus in the community was reduced substantially.
https://www.imperial.ac.uk/medicine/research-and-impact/groups/react-study/real-time-assessment-of-community-transmission-findings/Government figures released on Wednesday showed an additional 1,820 people had died within 28 days of a positive Covid test. To date, the U.K. has recorded 3.5 million coronavirus cases, with 93,290 deaths.
(...
equivalent to 10,750 deaths/day in the US ~100,000 in 9 days )
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Kids Highly Likely to Transmit Coronavirus to Others: Studyhttps://medicalxpress.com/news/2021-01-kids-highly-transmit-coronavirus.htmlWhile children are less susceptible to illness with the new coronavirus, they are nearly 60% more likely than adults over 60 to infect other family members when they are sick, a new study shows.
The researchers analyzed data from more than 27,000 households in Wuhan, China, that had confirmed cases of COVID-19 between Dec. 2, 2019 and April 18, 2020, a peak period of COVID-19 disease transmission in the city that was the first epicenter of the pandemic.
Previous research found that children shed SARS-CoV-2, the virus that causes COVID-19, at similar rates as adults. The higher infectivity of children in this study may be due to close contact with parents and other relatives caring for them, according to the authors of the study.
... The study also found that infants younger than 1 were significantly more likely to be infected with COVID-19 than children between the ages of 2 and 5. This may be due to a combination of their still-developing immune systems and their close contact with adults.
"It's unlikely there will be a vaccine for infants against COVID-19 in the near future, so we need to protect their caregivers," said study co-author Ira Longini, a professor of biostatistics at the University of Florida. "We may want to prioritize caregivers for COVID-19 vaccination to protect infants indirectly because we don't really know the long-term consequences of infection, especially in infants."
Among the other findings in the study:
- People who were asymptomatic during throughout their infection were 80% less infectious than people with symptoms, and presymptomatic people were about 40% more infectious than symptomatic ones.
- The secondary attack rate—the likelihood that a person with COVID-19 will infect another member of their household—was 15.6%, a rate similar to other respiratory pathogens.
- Older adults were more likely to become infected than younger household members, especially those under age 20.
While children were less susceptible to COVID-19 infection than adults and they generally had less severe symptoms, they were just as likely to develop symptoms as adults.
Household transmission of SARS-CoV-2 and risk factors for susceptibility and infectivity in Wuhan: a retrospective observational studyhttps://www.thelancet.com/journals/laninf/article/PIIS1473-3099(20)30981-6/fulltext--------------------------------------------
https://www.cdph.ca.gov/Programs/OPA/Pages/NR21-021.aspx