Five months after completing the course, the vaccine’s effectiveness in preventing infection drops to 30%. With the booster it goes back, even against the disease
Just a month ago, on November 26, the Omicron variant (B.1.1.529) appeared in several countries, including Italy, after South Africa and Botswana reported its existence to the World Health Organization on November 14. . The ECDC (European center for disease prevention and control) believes it could become prevalent in Europe within the first two months of 2022.
In Italy, according to the latest report from the Higher Institute of Health (Iss), dated 23 December, Omicron concerns 28% of the positives (albeit with strong regional differences) and the number of cases tends to double every 2-3 days . More precise indications on the prevalence estimates will arrive on December 29 and January 3, in two ISS flash surveys.
Even if the results are still preliminary, the estimate confirms the great speed of diffusion of the variant, which seems to give very widespread outbreaks in a short time and is about to become a majority, as is already happening in several other European countries – said the president Iss , Silvio Brusaferro -. Based on the data available today, the weapons available are vaccination, with the third dose timely for those who have already completed the first cycle, and individual and collective measures to limit the spread of the virus, from the use of masks to limitation. of contacts and gatherings.
From the first Omicron studies it also appears to cause more reinfections (generally not serious) than Delta, therefore the prudential measures and the importance of vaccination also apply to the recovered.
Protection drops to 30%
In Italy, over 85% of the over 12 population has completed the vaccination cycle and the booster has been administered to 55% of the subjects called to receive it today. Despite this, according to the latest ISS update, the weekly incidence of cases has been increasing for 9 weeks (also due to the high number of swabs performed every day, almost one million on 25 December): we are at 266 cases per 100 thousand. inhabitants, compared to 195 cases in the previous week. The mean Rt calculated on symptomatic cases was stable compared to the previous week: 1.13.
Infections (on Christmas day 55 thousand more than the previous day) are on the rise in all age groups, especially in the under 50 population. High incidence even in 6-11 years. Also according to the ISS report, 5 months after the completion of the vaccination cycle (2 doses or single doses), the effectiveness of the vaccine in preventing the disease, both in the symptomatic and asymptomatic form, drops from 71.5% to 30.1 %. The protection from severe disease remains high, from 92.7% to 82.2% in vaccinated individuals who have completed their cycle for more than 5 months. But here is the confirmation of the importance of the third dose: the effectiveness in preventing diagnosis and severe disease goes back to 71% and 94% respectively in subjects vaccinated with the booster. Not only that: according to the ISS, the risk of intensive care for the unvaccinated compared to those who have the third dose 85 times greater for those over 80, 12.8 times greater for the 60-79 age group, 6.1 times greater for 40-59 year olds.
Third dose at 4 months
The third dose can still be administered 5 months after the second (as well as the second dose for the recovered), but the Ministry of Health has already announced in a circular that the wait will be reduced to 4 months (starting from a date that it will be established by Commissioner Figliuolo in agreement with the Regions). Furthermore, from December 27, the third doses are extended to the age group 16-17 and to frail subjects between 12 and 15 years. In light of the current evidence on the epidemiological impact related to the greater diffusion of the Omicron variant and on the efficacy of the booster dose in preventing symptomatic forms of Covid-19, the administration of the booster dose will be possible after a minimum interval of at least four months from the completion of the primary cycle or from the diagnosis of infection is stated in the circular. The new variant pushes vaccinations, even among young people. The 20-29 age group has reached almost 91% coverage with the first doses, which are also growing in the 12-19 year-olds, where they have reached almost 80% – highlighted Brusaferro -. The number of over 80s who receive the third dose is growing significantly: we have reached 63-64% and at the same time this attention is growing in all age groups. It remains an important issue for people who have not yet started the vaccination course. They are still numerous and it is important especially in light of the Omicron variant to start the vaccination cycle.
Limited deaths and hospitalizations
Vaccination is important because today we are faced with very high transmission times and contagiousness – confirms the coordinator of the technical-scientific committee Franco Locatelli -. According to some studies, the Omicron variant would have five times higher contagious times than the Delta. If today we are able to contain the number of deaths and hospitalizations in intensive care thanks to vaccines. Indications from the UK show that Omicron is clearly neutralized by third dose vaccination coverage, at least by the risk of serious disease. Data that have led many countries to accelerate the administration of the booster: in France, for example, the Health Authority has recommended reducing the interval between the second and third dose to three months and vaccinating adolescents between 12 and 12 with the booster. and 17, more at risk of contagion. There is strong evidence that Omicron has a substantial growth advantage over Delta: it is spreading much faster, with a doubling time of 2-3 days – the World Health Organization points out -. It is still uncertain to what extent the rapid rate of growth observed since November can be attributed to immune evasion or increased transmissibility, but probably a combination of both.
The risk of reinfections
Omicron has increased reinfection rates: according to a study by the Imperial College of London, the risk of recurring the virus with the Omicron variant is 5.4 times greater than that of the Delta. It must be said that the infections linked to Omicron seem to involve a risk of hospitalization reduced by about 15-20% compared to the Delta and 40-45% less likely to be hospitalized for more than a day. This is demonstrated by another work from Imperial College London which examined all confirmed Omicron cases in England in the first two weeks of December. However, the authors explain, the large number of infections could still lead to a high rate of hospitalizations.
December 26, 2021 (change December 26, 2021 | 17:51)
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