The Ministry of Health has warned that “evidence is increasing” that the omicron variant of COVID-19 “escapes the immune response caused by previous variants and by vaccines.”
“Since the last update, numerous cases of omicron have been detected worldwide and the evidence is increasing that this variant escapes the immune response caused by the previous variants and by vaccines”, the Ministry collects in the update of the Rapid Assessment omicron risk, 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 that has been detected during the pandemic, which “raises a 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, CCAES experts detail that “several” of the changes in the sequence encoding the spicule protein (virus entry gate) of the omicron variant have been described previously and “are associated with the immune escape of the 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, CCAES technicians clarify that “the immunological escape potential of non-neutralizing antibodies and memory T cells directed at non-surface proteins is more difficult to determine.” In various studies, it has been shown that vaccines also increase patients’ T cells to deal with the virus, so that they 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 severe disease, even in situations where virus evolution leads to spike protein mutations that escape antibodies pre-existing neutralizers, “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 CCAES 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 the 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.
The CCAES stresses that “at this time, more studies are needed 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. “
What is the severity of those infected with omicron
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 symptoms.” Furthermore, no cases of serious illness, hospitalizations or deaths have been reported.
Despite everything, 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. Furthermore, the majority of cases detected in the EU / EEA for which data are available Until now they have been young or middle-aged people and they were fully vaccinated. As they are mostly travelers, it could also be assumed that they are healthier than the general population “, they maintain.
In line, they collect data from South Africa that indicate an increase in hospital admissions of COVID-19 cases in the province of Gauteng from 136 in week 45 to 279 in week 46 and to 647 in week 47, coinciding with the growing omicron predominance. “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 the CCAES.