Covid: the “circular” vaccination to combat the epidemic rebound?

The number of coronavirus cases is on the rise again. On Monday, March 21, 2022, the average number of cases within 7 days was nearly 89,700, compared to about 65,800 in the previous week.

The resumption of the epidemic can be explained by two main factors: first, the prevalence of the BA.2 variant, a subtype of Omicron. This virus is more contagious than the other variants. It soon became the majority in Denmark and replaced Omicron.

There are actually three sublines of the Omicron variant: BA.1, BA.2, and BA.3. But it was the Bibliotheca Alexandrina that benefited from several weeks in France and Europe.

The second factor: lifting restrictions on the state. Since March 14, it is no longer mandatory to wear a mask indoors (except for public transport and health institutions). On the same date, the vaccination card was suspended and only applies to health institutions and nursing homes. While residents appreciate this virtual return to normal, raising barrier gestures is conducive to the spread of the virus. Thus, for the emergence of possible new variants. Because the greater the spread of the virus in the population, the greater the risk of the variant appearing.

If the lifting of restrictive measures is encouraging, the epidemic is far from behind: Every week, new patients are hospitalized in intensive care and some die from a dangerous form of the coronavirus.

Vaccination in the “loop”, a new strategy to slow recovery from the epidemic?

Faced with what looks like a sixth pandemic wave, researchers from Inserm, Sorbonne University at the Pierre-Louis Institute of Epidemiology and Public Health in France, are considering new strategies.

One of them is to vaccinate the population in a “ring”.what does that mean?

In March 2022, nearly 80% of French people received at least two doses of the vaccine (and 53% received three doses). While the proportion of the population that has been fully vaccinated is high, the rate of people who remain reluctant or refuse to be vaccinated remains stagnant. However, in a context in which the pandemic could start again quickly due to variables, caution must remain in place. The emergence of new, more contagious variants also cannot be ruled out.

That is why the team of researchers proposes to carry out “reactive” or “loop” vaccination: it is a question of vaccinating the entourage of a person who has tested positive. This strategy consists of providing vaccinationCases of direct contact with the injuredAt home and at work or school.

This strategy has already been used during certain Ebola epidemics in order to limit the spread of the virus. In order to be successful, effective contact case tracing must be done. But is this method appropriate in the context of COVID-19?

To find out, the researchers wanted to test this model in several epidemiological scenarios. They incorporated various criteria such as socio-demographic characteristics, social contacts and occupational statuses of the population of a medium-sized French city.

They also added to this the vaccination coverage rate, the efficacy of vaccines, and restrictions on contacts or establishing contact tracing.

What is the effect of the “circular” vaccination strategy?

According to the researchers’ models, the application of “circular” vaccination is more effective than the strategy of mass vaccination in various epidemic scenarios.

If we take the example of vaccination coverage of 45% and the spread of the virus significantly, the decrease in the number of cases goes from 10% to 16% over a period of two months with circular vaccination.

Note, however, that this method is more effective in poorly vaccinated populations. But this is not the case in France. But even in our country, this strategy can be useful. It can help convince people who have not yet been vaccinated of the benefit of the vaccine. “The fact of exposure to the virus increases risk perception and tends to make vaccination more acceptable,” identified the authors of the study devoted to this topic and published in the journal.Nature Communications.

Moreover, this strategy can be very effective in the event that a new, more contagious variant emerges. Reactive vaccination can increase vaccination coverage in a country, reduce the number of cases in certain epidemiological scenarios such as the emergence of a variant, and should be associated with accurate tracing of contact cases. Thus, any booster doses can be administered more intelligently and as a priority to the public in direct contact with the virus.

source:write contactsMarch 2022.