Bivalent vaccines against Covid-19 impact the fight against the disease in the US and Europe

Pharmaceuticals such as Pfizer and Moderna have developed updated, so-called second-generation, Covid-19 vaccines that are bivalent – ​​that is, they protect against the original strain of the coronavirus as well as against Omicron, including subvariants such as BA.1, BA .4 and BA.5.

Pfizer’s bivalent immunizers were approved by the National Health Surveillance Agency (Anvisa) in November 2022. The Ministry of Health announced that vaccines will begin to be applied in the country from February 27, in priority publics, as a strategy to reinforcement (see list here).

Pfizer’s bivalent BA.1 vaccine is approved in at least 35 countries. The bivalent version BA.4/BA.5 is approved in 33 countries, such as Canada, Japan, United Kingdom, United States, Australia and Singapore, among others, in addition to the European Union.

Moderna’s bivalent vaccine was also authorized for use in the United States in 2022.

Results on the effectiveness of immunization with bivalent doses are recent and are being released as they become available.

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Monovalent vaccines against Covid-19, widely used since the end of 2020, were developed from the original strain of the coronavirus, identified in Wuhan, China.

Over the three years of the pandemic, the SARS-CoV-2 virus, which is responsible for the disease, has continued to evolve. The increase in viral circulation favors the accumulation of mutations and the emergence of new strains of the coronavirus.

With the evolution of the virus and the emergence of worrying variants, such as Omicron, scientists are studying in real time the impact of strains and mutations on the effectiveness of vaccines.

During vaccine development, analyzes are conducted to demonstrate the efficiency of immunizers from controlled trials.

After the approval of Organs regulatory bodies and the beginning of the application in the population in a broad way, the continuity of the studies points to the effectiveness rate which consists of the protective impact of immunizers in the face of what scientists call “real life” because they reflect the results of vaccination in practice in large populations.

First studies in the United States

The Food and Drug Administration (FDA), an agency similar to Anvisa in the United States, approved the emergency use of bivalent vaccines from Pfizer and Moderna on August 31, 2022. According to the FDA, the recommendation is for use as a single dose booster at least two months after primary or booster vaccination.

In recent weeks, the United States has faced an increase in the number of cases of Covid-19 driven by the circulation of a subvariant of Omicron, called XBB.1.5, which is highly transmissible.

The first results on the effectiveness of booster vaccination with bivalent doses in the United States are now being released.

The US Centers for Disease Control and Prevention (CDC) announced in a study that updated booster doses reduce the risk of illness from Covid-19 by about half, even in the face of infections caused by the XBB.1.5 subvariant.

To estimate the effectiveness of bivalent vaccines against symptomatic infection, CDC scientists analyzed data from the Access to Testing Program (ICATT) between December 1, 2022 and January 13.

Of 29,175 tests of adults aged 18 to 49 analyzed, 13,648 were positive for the SARS-CoV-2 virus, including 10,000 related to BA.5, and just over 3,000 related to the XBB or XBB.1.5 subvariants.

The analysis showed that booster with second-generation vaccines reduced the chances of symptomatic infection caused by subvariant BA.5 by 52%. In the case of disease caused by the Omicron XBB or XBB.1.5 subvariants, the index decreased slightly to 49%.

For the 50- to 64-year-old population, the updated boosters reduced the odds of falling ill with Covid-19 by 43% for BA.5 and by 40% for XBB subvariants. For those aged 65 years and older, boosters reduced the odds of an infection with symptoms by 37% and 43% for BA.5 and XBB subvariants, respectively.

Despite the preliminary results found, estimating the impact of vaccination with bivalent doses in the United States remains a challenge.

According to CDC data, only 15.5% of the US population has received the updated boosters to date. In numbers, just over 33 million of Pfizer’s bivalent doses and 18.7 million of Moderna’s second-generation immunizers were applied.

Since the approval of bivalent vaccines by the FDA, the numbers of cases, deaths and hospitalizations for Covid-19 in the US have varied, with periods of high and low.

The latest data on deaths from the disease from the CDC, on January 25, point to a total of 3,756 weekly deaths – the second consecutive week of decline.

Since the beginning of January, the total number of cases registered weekly shows a decrease. In the last week counted, with data from January 25, 295,140 cases of the disease were registered.

The daily count of hospital admissions has shown a downward trend since the beginning of January. The survey for the period from January 18 to 24 shows an average of 4,216 hospitalizations for the disease in the country. In the previous week, the average reached 4,897 hospitalizations due to the coronavirus infection.

Epidemiological scenario of Europe

The European Medicines Agency (EMA) approved the use of the first updated vaccines for the Ômicron variant in September 2022. Four second-generation immunizers are applied, two of which are from Pfizer (BA.1 and BA.4/BA. 5) and two from Moderna (BA.1 and BA.4/BA.5).

The most recent data on Covid-19 on the European continent, referring to the third week of January, point to a continuous general improvement in the epidemiological situation.

According to the European Center for Disease Prevention and Control (ECDC), the combined rates of case notifications, hospital admissions and deaths continued to decline after increases seen in December, both in the general population and in long-term care facilities. permanence.

Of the 28 countries that reported case notification data through week 3, which ended Jan. 22, none reported increasing trends, according to ECDC.

Only one of the 21 countries with data on intensive care unit (ICU) admissions and occupancy reported increases in at least one of the indicators, while two of the 26 countries that reported data on Covid-19 deaths reported increases.

These increases were recent (1 to 2 weeks in duration) and the indicators remained relatively low in the affected countries.

The ECDC warns that the picture of improvement must be monitored carefully. In the last week evaluated, 1,311 deaths from Covid-19 were reported by 26 countries in the European Union.

In the past four weeks, 27% and 63% of deaths for which age was reported occurred in people aged 65 to 79 years and 80 years and older, respectively.

The application rates of the first booster dose range from 11 to 87% among adults aged 18 years and over, with an average of 65.4%. Among seniors aged 60 years or older, the rate is between 13 and 100%, with an average of 84.9%.

Considering the total population, the first reinforcement was given to 54.7% of individuals, with a variation from 9 to 75% between countries.