Oxford vaccine against Covid is the first to have a phase 3 trial published in a scientific journal | Vaccine

The data, which are still preliminary (because the tests are not over yet), had already been launched in November: the vaccine showed an average effectiveness of 70.4%, with up to 90% effectiveness in the group that took the lowest dose.

In practice, if a vaccine is 90% effective, it means that 90% of the people who receive the vaccine are protected against that disease.

Publication in a scientific journal means that the test data has been reviewed by other scientists and validated. It does not mean that the Oxford vaccine will be applied immediately to the general population..

For this, it must still be approved by the regulatory bodies – in Brazil, this body is Anvisa; in the UK, the Medicines and Health Products Regulatory Agency (MHRA).

The Oxford vaccine is one of four being tested in Brazil: 30 million doses must be received by the end of February; another 70 million in July. The forecast is for another 110 million doses to be produced in the second half of 2021.

This Tuesday, during a meeting with governors, Health Minister Eduardo Pazuello said that the forecast is for the Oxford vaccine registry to be ready by the end of February.

On Tuesday, the British began immunizing against Covid-19 with the vaccine developed by Pfizer, which was approved last week.

Highlights of Oxford Ads

• The effectiveness analysis was carried out jointly and considers data from trials in the UK and Brazil.
• The vaccine was safe and effective against the disease. no hospitalizations or severe cases of Covid-19 in the vaccinated groups. In the groups that did not receive the vaccine, there were 2 severe cases of Covid-19 and one death.
• The vaccine had 90% effective when given in half the dose followed by a full dose at least a month apart, based on UK test data.
• When given in 2 full doses, the efficacy was 62%.
• The analysis that considered both types of dosage indicated an average effectiveness of 70.4%.
• To arrive at the results, the researchers analyzed data from 11,636 vaccinated people. Of these, 8,895 received the two full doses and 2,741 received half the dose followed by a full dose. (See the details of the distribution of Covid-19 cases below).
• Approximately 88% of the volunteers analyzed (10,218) were between 18 and 55 years old.
• No participant aged 56 years or older received half the dose followed by the full dose, which was more effective (see details below).
• The effectiveness of the vaccine has not been evaluated in participants older than 56 years, but will be determined in future analyzes.
• Researchers are investigating the vaccine’s potential to prevent asymptomatic cases of Covid-19.

Methodological caveats

Two study points previously announced on November 23 had already been subject to expert reservations. In the first, the researchers who did not participate in the tests indicated that greater rigor would be necessary to calculate the effectiveness of the vaccine considering different tests in Brazil and the United Kingdom.

The AstraZeneca / Oxford researchers denied that the differences between the two clinical trials detract from the analysis.

“Despite small differences between studies, there is enough consistency to justify the pooled data analysis proposal, which will provide greater precision for efficacy and safety results than can be achieved in individual studies and provide a broader understanding. of vaccine use in different populations, “the researchers said in the article.

Another criticism of the Oxford scientists was the fact that the lowest and most effective dose was administered only to volunteers between the ages of 18 and 55.

Critics pointed out that the greater efficacy observed in this group could be due to the age of the group and not necessarily to the dose applied.

This is because younger people tend to respond better to vaccines than older people.

Researcher Andrew Pollard, who led the study, said Tuesday that scientists had analyzed the effectiveness data by considering the age of the participants. According to Pollard, when the researchers compared only data from participants of the same age, between groups that received different doses, greater efficacy continued to appear at the lower dose. In other words: age was not a factor for the effectiveness to have been greater.

In total, the researchers saw 131 cases of Covid-19 among the 11,636 participants, distributed as follows by dose:

• 8,895 people participated in these tests.
• Of these, 4,440 took both doses of the vaccine. The other 4,455 took a placebo (inactive substance).
• Among those who received the vaccine, there were 27 cases of Covid-19. Among those who took a placebo, 71.

HALF DOSE + A FULL DOSE:

• 2,741 volunteers participated in these tests.
• Of these, 1,367 took half the dose followed by the full dose. The other 1,374 took a placebo (inactive substance).
• Among those who received the vaccine, there were 3 cases of Covid-19. Among those who took placebo, there were 30, ten times more.

In the trials, half of the participants received the Covid-19 vaccine and the other half received a placebo (meningitis vaccine or saline). The study was designed to evaluate a single dose of the vaccine, but after reviewing the data from phases 1 and 2 in the UK, another dose was added to the test protocol.

Of the 131 cases of Covid-19 registered 14 days after the second dose of the vaccine, 30 cases were in the vaccine group and 101 cases in the control group. There have been five cases of coronavirus in people over 55 years of age, but the efficacy of the vaccine in older ages has not been evaluated, as there were few cases. The authors say that this analysis will be completed in the future.

“To assess the effectiveness of the vaccine, we need to have a sufficient number of Covid-19 cases among the participants to indicate that the vaccine is protecting. The recruitment of older people started later than in younger adults. That means we have We have to wait longer to have enough data to provide good estimates of vaccine efficacy in smaller subgroups, “said one of the study’s authors, Merryn Voysey from the University of Oxford.

The study also measured protection against asymptomatic infection, but the researchers explain that the data are secondary and need further study.

69 cases of asymptomatic disease were recorded in a group of 6,638 participants in the UK: 0.9% of cases in the vaccine group and 1.2% of cases in the placebo group, leading to a efficacy against asymptomatic transmission of 27%.

In the low-dose group, the efficacy against asymptomatic transmission was 59%. In people with two standard doses, the rate was 4%.

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