Friday , March 5 2021

Covid-19 vaccines: How fast can covid-19 vaccination vary? | Science and technology

HHOSPITALS AROUND the world, once again, flows under a torrent of covid-19 patients. In places as far away as London, Cape Town and Los Angeles, ambulances have waited hours to unload the sick and refrigerated trucks have been taken to contain the dead. Vaccines are the only way out. The question is, how quickly can they turn things around?

Vaccines reduce deaths and hospital admissions in two ways: they directly protect vaccines, preventing them from getting sick; and offer indirect protection to people who are not vaccinated, as those infected are less likely to have people who are already vaccinated. Measuring the combined effect and how quickly it starts is only possible when mass vaccination is underway. But the first results are beginning to come.

Most countries vaccinate their seniors first, along with health workers. The preponderance of covid-19 deaths (around 85% in England, for example) correspond to people aged 70 years or older (see Figure 1). People in the covid-19 hospital wards are also this age. Therefore, hospital admission rates and deaths should drop sharply within a few weeks after a large portion of the elderly received their first punch. However, hospitals will fight until a large number of middle-aged people are also vaccinated. This is because, at the moment, the worst pressure is on intensive care units (UCIs), and most of these patients are between 50 and 60 years old. This may seem strange, given the higher mortality rates among the elderly. But fans and other organ support machines put a lot of strain on the body, and older people are often too fragile to fit. Covid UCIEnglish hospitals, for example, currently treat as many patients aged 20 to 49 as patients aged 70 or older.

This pattern means that when vaccination is slow, the number of deaths related to the covide of middle-aged people may increase in the coming weeks and months, UCIs omple. Typically, these units have one nurse per patient. However, more and more, UCI nurses have to care for several patients each. Two recent studies, one from England and one from Israel, have concluded that when it comes to covidi UCIThey were observed to be filled to the maximum capacity, mortality in them was 20-25% higher than would have been expected given the characteristics of the patients involved.

Massive observation

With this for many countries, Israel is the place to look at the first evidence of how mass vaccination can change things, as it has vaccinated its citizens faster than anywhere else. On January 19, a month after the campaign began, Israel had given 26% of its 9 million people at least one dose. As has happened elsewhere, it started with seniors. And for them, some results are now emerging.

In a recent analysis, Ran Balicer of the Clalit Research Institute in Tel Aviv and his colleagues compared, on a day-to-day basis, a group of 200,000 people over the age of 60 who had been vaccinated with a group of individuals. who were not vaccinated. Differences in infection rates between groups were tracked by comparing test results for people who tested for covid after reporting relevant symptoms or close contact with someone who had previously given positive.

During the first 12 days of the study, positive test rates remained identical between groups. On the 13th, the rate of the vaccinated group fell slightly. Then, on the 14th, a third fell. There has been some disappointment that this drop has not been major, but the vaccine in question, the Pfizer-BioNTech offering, is scheduled to be given in two doses, so the picture will not be clear until second doses are not administered and results from younger people have also been included.

The early effect on hospital admissions of Israel’s mass vaccination campaign has been more difficult to measure, due to two confusing variables: the country’s national blockade, which tends to reduce the rate regardless of the effect of vaccines and the spread of B.1.1.7, a variant of the virus first found in Britain, which is much more contagious and therefore tends to increase the rate. This combination of factors, however, is also being experienced in many European countries and parts of the United States, so what is happening in Israeli hospitals now is a harbinger of what these other places can expect in the coming weeks and months. .

A sign that vaccination is beginning to give some respite to Israeli hospitals came a fortnight after Jan. 2, the day the proportion of people over 60 vaccinated reached 40 percent. The number of critically ill patients with covid-19 in this age group grew by approximately 30% the week before January 2 and also the following week, but only by 7% the following week (see Figure 2). In contrast, among people aged 40 to 55 (vaccinated at a much lower rate at the time), the weekly change in the number of critically ill remained constant, with an increase of 20-30% in each of these three weeks.

Taking such early results in an epidemic trajectory model, Eran Segal of the Weizmann Institute and colleagues estimate that deaths from covid-19 in Israel could begin to decline in early March, even if the closure ends, as planned, last week. January. Its prognosis assumes that the vaccination rate is maintained and that 80% of adults receive their second dose at the end of February. (The other 20% are people who cannot be vaccinated for reasons such as allergies or who refuse to vaccinate them).

Do children suffer?

Even a campaign as effective as Israel’s, however, leaves many neckless. In addition to refuseniks and adults who cannot be vaccinated, no covid-19 vaccine has yet been approved for use in children. Children rarely get sick if they are infected, but they can still transmit the virus. This can lead to future outbreaks, albeit less widespread.

Usually, vaccine trials in children start with the older ones and continue to go down. Clinical trials of several covid-19 vaccines have begun in children up to 12 years of age and results may be available in the summer. However, trials in those minors of this period will take longer. Therefore, a covid-19 vaccine is unlikely to be approved for most children before 2022. Until then, curbing the pandemic will be difficult if many adults refuse to roll up their sleeves to give themselves of eye.

This article appeared in the Science and Technology section of the print edition under the title “The Time Has Come”

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