Health confirms “evidence” that omicron “escapes immunity”

“Since the last update, they have been detected numerous cases of omicron worldwide and there is increasing evidence that this variant escapes the immune response caused by previous variants and by vaccines “, the Ministry collects in the update of the Rapid Risk Assessment for omicron, published this Friday.

The report, signed by the Center for the Coordination of Health Alerts and Emergencies (CCAES), led by Dr. Fernando Simón, points out that omicron “is the most genetically divergent” of those detected during the pandemic, which “raises great concern that it may be associated with a significant reduction in the effectiveness of the vaccine and an increased risk of reinfections.”

In this regard, the experts from the Health Alerts Center detail that “several” of the changes in the sequence that encodes the spicule protein (gateway of the virus) of the omicron variant have been described previously and “are associated with immune escape of neutralizing antibodies or other properties“.

At this point, they cite the example of a previously described synthetic variant with 20 mutations in the spike protein that “was associated with an almost complete escape from neutralization by convalescent and vaccinated sera“As omicron carries even more mutations in the S gene compared to the synthetic variant, a very significant effect on neutralization is expected”, warn the technicians.

Protection by T cells?

However, the technicians of the Center for Health Alerts clarify that “the potential for immune escape of non-neutralizing antibodies and memory T cells directed to non-surface proteins is harder to determine“In various studies, vaccines have also been shown to increase patients’ T cells to deal with the virus, so that you could have a different type of immunity to antibodies.

“Memory T-cell responses may offer a pathway to long-lasting immunity and protection against the development of serious disease, even in situations in which the evolution of the virus leads to mutations of spike proteins that escape pre-existing neutralizing antibodies “, they argue.

The report collects data from a reinfection analysis in South Africa that has analyzed epidemiological surveillance data with 2,796,982 cases with samples between March 4, 2020 and November 27, 2021. Although increases in the risk of Primary infection after the introduction of the Beta and Delta variants, a corresponding increase in the risk of reinfection was not observed.

In contrast, the recent spread of the omicron variant has been associated with “a decreased risk of primary infection and an increased risk of reinfection“.” This finding, if confirmed, would have important implications for public health planning, particularly in countries like South Africa with high rates of immunity to previous infections, “the experts emphasize.

The center also gives as an example a preliminary examination of the data of admitted in the South African province of Gauteng. Of a total of 347 patients with available information on their vaccination status, 317 correspond to vaccinated and 30 to non-vaccinated.

“Although this is very preliminary data and could be affected by different biases, if the percentage of vaccinated population in South Africa is taken into account, of around 25 percent, these data suggest that vaccines would offer a significant degree of protection against serious infection since the percentage of vaccinated among those admitted is considerably lower than that expected if the vaccine did not offer protection “, they argue.

Likewise, he emphasizes that “at this time, more studies are necessary on neutralization ‘in vitro’, the effectiveness of the different vaccines, as well as additional data on the risk of reinfection in people with previous immunity and the severity of reinfection in exposed populations. to different variants of SARS-CoV-2 during previous pandemic waves. ”

Omicron effects

The document reassures about the seriousness of the cases, as it alleges that of all the cases reported in Europe with omicron “half of the cases were asymptomatic and the other half had mild symptomsFurthermore, no cases of serious illness, hospitalizations or deaths have been reported.

Nevertheless, Health called prudence because “at the moment there are still few cases detected and they are also very recent”. “Severity outcomes often take several weeks to see and more time to become apparent at the population level, which would affect hospital occupancy rates. Additionally, the majority of detected cases for which data is available so far have been people. young or middle-aged and were fully vaccinated. Being mostly travelers, it could also be assumed that they are healthier than the general population, “they maintain.

On the wire, they collect data from South Africa that indicates an increase in hospital admissions for Covid-19 cases in Gauteng province from 136 in week 45 to 279 in week 46 and to 647 in week 47, coinciding with the growing prevalence of omicron. “While case rates are increasing faster than in previous waves in Gauteng province, hospitalization rates are in line with previous increases,” they say.

On the other hand, they recall that the previous circulation in South Africa of Beta, the most divergent variant detected before omicron, “could potentially lead to a less serious disease in this population.” “Current estimates on the severity of Covid-19 cases caused by omicron remain highly uncertain and more studies are needed, including longer-term follow-up by age group, previous infection, and vaccination status of identified cases, to provide more reliable estimates, “concludes CCAES.