sharp decline in effectiveness with two doses – breaking latest news

The weekly report on the epidemiological situation in the UK compiled by the UK was released on Friday UK Health Security Agency (UKHSA) which contains extensive insights into the variante Omicron.

Cases on a steep rise

Cases of the Omicron variant in the country are growing rapidly: the latest figure stands at 696 and is underestimated due to the diagnostic delay due to the need to sequence suspected cases to confirm them (across the EU there are 582 cases from 21 countries). The real Omicron positives would be 7,000 in all, based on the S gene exclusion tests: 8.5% of the total. In the graphs compiled by the Agency, one notices steeper growth curve (i.e. faster) of Omicron compared to the first weeks recorded by the other variants that have appeared in the UK (see GRAPH 1 above, ed). The provenance of the positives is not linked to recent travels, so it is almost entirely due to internal transmission.

Marked decline in efficacy

In a graph onvaccine efficacy (see above GRAPH 2, ed) UKHSA shows the efficacy of two vaccine combinations against Omicron (symptomatic) infection. These are still small numbers (and therefore not definitive), but important, because so far the resistance of vaccines against Omicron has been “only” measured with laboratory experiments, which have suggested a certain evasive capacity of the variant to be confirmed in the real world. . What does the report from the UK say? Vaccination efficacy (towards symptomatic infection) undergoes a significant decline between Delta and Omicron: in the formula with the two doses of AstraZeneca, after six months it turned out pari a zero and equal to 34% with two doses of Pfizer. A much greater decline than that seen with Delta after about 5-6 months from the two doses. The data are preliminary, the numbers low (581 cases) and the confidence intervals large (range of plausible values ​​for that given parameter, ed), but they are not reassuring numbers.

Third effective dose

The good news is that the third dose (in this case given by administration of Pfizer) balances the situation by bringing those vaccinated with AstraZeneca as the primary course to an efficacy of the 71% and those with three doses Pfizer al 76% in the first month following inoculation (see the numbers of the graph shown in detail in TABLE 1 above, ed).
While it’s not the 95% offered by the third dose with the Delta, it’s considered good value, especially since it’s still being talked about protection against contagion. All vaccines in use have always had higher protection values ​​towards hospitalizations and deaths than those concerning efficacy towards infection. It is expected that it will be the same for Omicron, although we don’t know yet.

Immune evasion

A share of the loss of neutralizing capacity by the vaccines towards the variant, however, is now quite delineated. The UK report examines the first evidence of Omicron’s ‘immune evasion’ ability to come from laboratories: according to 2 UK and 3 international studies on how people behave antibodies from fully vaccinated people (with Pfizer), compared to Omicron there has been a 20-40-fold reduction in virus neutralization (compared to previous variants of SARS-CoV-2) and 10 times compared to Delta. Antibodies aren’t the only indicator of protection, though, and the results are very preliminary.

Less aggressive virus?

The report also shows that in the UK there are no hospitalizations or deaths associated with Omicron, however, there are very few cases in high-risk groups, including the elderly. However, the positive figure would confirm the analyzes coming from South Africa, where, of the Covid positive patients admitted to hospitals in Pretoria, 31% required specialist care or intensive care compared to two thirds of the patients in the previous waves.
Omicron looks milder, but it is not yet said it really is. It could only be so in appearance, as explained on Twitter by Natalie E. Dean, professor of Biostatistics, specializing in infectious diseases and vaccines at Rollins school of public Health: the denominator for calculating severe cases also includes reinfections, the portion of severe cases is not lower, therefore, because there are fewer severe cases, but because there are more mild cases (reinfections + mild cases).

A very contagious variant

The bad news that seems to be confirmed concerns thehigh transmissibility of Omicron, which may be greater than Delta and even rated 500 times higher than the original Wuhan strain.
Omicron has capabilities of also reinfect the vaccinated and confirmation comes from 7% of Omicron cases classified as ‘reinfections’ by the English report, which means an increased risk of resuming Covid from 3 to 8 times compared to what happened with Delta.
In the British Agency’s analysis, 19% of Omicron cases resulted in family outbreaks versus 8.5% of Delta cases. The “secondary attack rate” (that is, the proportion of secondary cases that develop through close contact with a primary case, ed) measured in the family is 2 times higher for Omicron (21.6% in the report data) than for Delta (10.7%).
That’s why the forecast for the UK sees a growth doubling time of Omicron cases of 3 days and they write that the variant will reach parity with Delta by mid-December.

In Scotland doubling time is estimated at 2.3 days and Omicron could represent 90% of cases in about 7 days (data from the local government report, see GRAPH 3 above, ed). According to some analyzes, Scotland could be around 1 week ahead of England in terms of Omicron broadcasting.
In conclusion, what can we say about the “new” variant that worries the world? Omicron spreads faster and is able to escape immunity better than other variants. Its severity is still unknown, although vaccination is likely to reduce severe disease. The data are few and preliminary and for further confirmation we need to wait a little longer and get the third dose of vaccine as soon as possible.