See what is known about the Omicron subvariants BA.4 and BA.5

Two new subvariants of the omicron, BA.4 and BA.5, have marked the current evolution of the Covid-19 pandemic in the world. First identified in South Africa earlier this year, they are associated with a new wave of infections in the African country that peaked in May.

BA.4 and BA.5 are also associated with a new wave in Portugal, where more than 90% of cases are due to the two new subvariants and there was an increase in the number of infections and hospitalizations.

Several other European countries see BA.4 and BA.5 gaining ground over the other subvariants. The European Center for Disease Prevention and Control (ECDC) predicts that they will soon become the dominant sub-variants in the European Union and are expected to trigger an increase in the number of new Covid-19 cases in the coming weeks.

Brazil is also in what could be the beginning of a new wave of the pandemic and since the end of May it has been registering an increase in the average of new daily cases. As in South Africa and Portugal, BA.4 and BA.5 may be behind this trend.

An analysis by Instituto Todos pela Saúde (ITpS) made with data from Dasa and DB Molecular and published by the newspaper O Globo on Friday (10) showed that the proportion of probable cases of the two new subvariants increased from 10.4% to 44. % in four weeks.

The average of new daily cases in Brazil, in the period of seven days, has been high for more than two months. On Monday, it was at 43,131, a level comparable to the beginning of March.

In the count by epidemiological week, week 23 of this year, from June 5 to 11, recorded 292,000 new cases. The last time this number had been surpassed was in week 10, from March 6 to 12, when 317,000 cases were reported.

There was also a rise in the number of new deaths. The daily moving average of deaths, in the seven-day period, is at 163, a level that has not been surpassed since the beginning of April.

Some epidemiologists and scientific communicators, such as Átila Iamarino, have been warning of the need to maintain care, such as wearing a mask indoors, to face a possible new wave of the pandemic.

What is known about BA.4 and BA.5:

when they emerged

Both were first detected in South Africa – BA.4 in January and BA.5 in February. In May, they made the variants dominant in that country, which saw an increase in the numbers of new cases and the percentage of positive tests in the same period.

Epidemiologists consider that BA.4 and BA.5 were responsible for the increase in new cases registered in South Africa during the months of April and May. In the African country, the peak of the new wave occurred in mid-May.

what is different

BA.4 and BA.5 have spike protein mutations of the same genus as those that characterize all omicron subvariants, and are similar to the BA.2 subvariant, still prevalent in Europe. In addition, they have additional mutations in other parts of their genome.

The evolutionary advantage of BA.4 and BA.5 that has allowed it to gain space over BA.2 is probably due to a greater ability to evade the immunological protection provided by a previous infection or vaccination, especially if the protection of the vaccine has dropped over time.

What the polls say

Preliminary laboratory test results indicated that blood serum from individuals vaccinated with three doses of Pfizer-Biontech or Astrazeneca vaccine was less effective at neutralizing BA.4 and BA.5 than BA.1 and BA.2 .

The same was verified with the serum of patients who had already been infected once with BA.1.

Therefore, there are indications that BA.4 and BA.5 are more effective in infecting people who have already been vaccinated or who have had Covid-19 before. The current wave in Portugal, for example, has registered an increase in the rates of reinfection by the disease.

There are still no data on the effectiveness of vaccines against Covid-19 in relation to BA.4 and BA.5.

Is it more severe?

So far, there is no indication that BA.4 or BA.5 have more severe effects than the other subvariants of the omicron.

In Portugal, where BA.5 already accounts for almost 90% of new infections, several indicators, such as hospitalization rate, ICU admissions and number of deaths, were on June 1st below the levels recorded in previous peaks of the omicron.

However, there is a weekly increase in these numbers in Portugal, with the increase in the rate of hospitalization and ICU admissions, concentrated in patients aged 60 years and over.

In South Africa, the wave of BA.4 and BA.5 had a “much, much less fatal impact than any of the previous waves,” virologist Tulio de Oliveira of the University of Kwazulu-Natal said on Twitter.

He points to the high immunity of the population from vaccines or previous infections and the fact that the wave started with a high number of beds available in hospitals as reasons.

​Situation in Europe

BA.4 and BA.5 were first identified in the European Union in March, and the first country where they became dominant was Portugal.

In recent weeks, there has been an increase in the participation of BA.4 and BA.5 in new cases of Covid-19 in several European countries, including Austria, Belgium, Denmark, France, Germany, Italy, Netherlands, Spain and Sweden. .

In Belgium, for example, BA.4 and BA.5 already account for around 27% of new cases.

In Germany, BA.4 and BA.5 account for 12.1% of new infections, while BA.2 still dominates with 87.5% of new cases, according to the June 9 bulletin of the Robert Koch Institute, the agency government for the control and prevention of diseases. The German Minister of Health, Karl Lauterbach, reinforced that the subvariants could be responsible “for a new wave in the autumn”.

The ECDC says the intensity of the increase in new cases expected in the coming weeks in the EU will depend on several factors, including immune protection related to vaccination coverage and the timing of doses and contamination rates from previous waves of the pandemic.

Although there is no evidence that BA.4 and BA.5 are more severe, the increase in the number of cases may lead to an increase in hospitalizations, ICU admissions and deaths, as occurred in previous waves.