The data obtained in countries that manage to push the mass immunization of their populations against Covid-19 shows that the vaccines available today can defeat the coronavirus.
In all of these locations, hospital falls and deaths followed more or less the same pattern, which benefited the early vaccine groups – generally the elderly – relatively early and intensively. The decrease in cases is still not as evident, partly because not all vaccines can prevent transmission of the virus, but it has also occurred.
The most striking example for now is that of Israel, where around 80% of residents have already received at least the first dose of the vaccine made by the pharmaceutical company Pfizer (a feat that is in part facilitated by the population of Israel only 9 million residents). Since the peak of the pandemic in mid-January 2021, Covid-19 cases have decreased by 98% and deaths have decreased by 87%.
Israel’s swift vaccination coincided with a nationwide month-long lockdown (from early January to early February) that certainly also helped slow the transmission of the Sars-CoV-2 coronavirus in the country. However, a new analysis published in the journal Nature Medicine has managed to separate the positive effects of restricting people’s circulation from those caused by the vaccines themselves.
In the study, scientists led by Eran Segal of the Weizmann Institute of Science suggest that the effects of the Israeli lockdown should be more or less uniform (as there are little regional differences) within regardless of people’s age and geographic location of the small territory of Israel).
On the flip side, as in Brazil, vaccination followed age priorities (first to the elderly who are at higher risk of hospitalization and death) and also some cities in Israel were vaccinated a little earlier than the others. These two factors could therefore serve as a “natural experiment” on vaccine effectiveness that was administered in the country in late December 2020.
Based on data collected between August 28, 2020 and February 24, 2021, the researchers were able to compare not only the situation of age groups and cities with and without vaccines, but also the scenarios of two different lockdowns (since Israel is already in isolation introduced in September 2020).
As expected, Israelis aged 60 and over benefited earlier and more intensively in early 2021. Compared to people aged 20 to 39 years, the proportion of positive tests that indicate an infection with Sars-CoV-2 decreased by 45% in the elderly (against 28% in the younger group); Similarly, hospital stays over 60 years decreased by 68% (compared to only 22% for younger people).
Similar, though less intense, was seen in cities where vaccination began at different rates. Those who received the vaccine first had a decrease of 88% in cases and 79% in hospitalizations, versus 78% and 66% in places where the vaccine arrived a little later, respectively.
Segal celebrated the results on his Twitter account. “Vaccines have practically eradicated Covid-19 in Israel, at least for the time being,” he wrote.
“They are solid data. The main signal of protection [trazida pela vacina] is that cases and hospital stays for groups vaccinated over the age of 60 fall below the expected curve for lockdown, ”says Brazilian immunologist Rafael Polidoro, postdoctoral fellow at Indiana University (USA).
A similar pattern, although with less impact on the number of cases, is developing in the UK (49% of the population have received at least one dose of vaccine) and the US (39%). In the British case, the positive effect occurred successively in the age groups between 90 and 60 years and can already be observed in the group between 50 and 60 years.
Everything indicates that the effect occurs not only thanks to the superior effectiveness of RNA vaccines (“raw” DNA molecules), a technology that is used in vaccinations by Pfizer and also by the American company Moderna and whose effectiveness is 90% exceeds. Data from Chile, a country that has already offered at least the first dose of vaccine to about half of its adult population, also shows a decrease in hospital admissions in the elderly, even in a scenario of increasing cases, hospital admissions and deaths in the youngest.
Approximately 90% of vaccinated Chileans received Coronavac, made with inactivated virus, which is also the main immunization against Covid-19 in Brazil. The protection offered by the vaccine is less than that of RNA vaccines (67% of symptomatic cases, according to the Chilean government) and only quite modest with the first dose. These factors, on top of the few restrictions placed on the Chilean movement in early 2021, likely explain the country’s recent problems with the pandemic.
Everything indicates that the strategy that will most improve the effectiveness of vaccines in the population is to combine rapid immunization programs with severe mobility restrictions.
And it is possible that at least initially there will be an annual vaccination against Covid-19 like the vaccination against influenza annually. “Before the pandemic, there was already a discussion that it would be important to have a vaccine against all coronaviruses and that this vaccine could be annual,” says immunologist Cristina Bonorino of the Federal University of Health Sciences in Porto Alegre. “The memory that provides lifelong protection against infection is still pretty mysterious. I’m sure immune memory specialists need to think about how to do this with vaccines for Covid-19, but we won’t have that right away. “
“Coronaviruses change relatively little over time, but that time can be sped up if transmission stays as high as in Brazil,” warns Polidoro. “It’s not convenient to keep transmission high during vaccination. In this case, we cannot count on luck. “We are a family business.