In recent weeks, Costa Rica has seen an increase in cases of the Covid-19 virus, which for professionals represents a new epidemic wave, characterized by an acceleration of the infection rate and an increase in the number of hospitalizations of minors.
How long will this pandemic wave last? How many cases can we wait in the next few months? The Center for the Central American Population of the University of Costa Rica (CCP-UCR) has developed two scenarios according to the dynamics of the virus and how it might affect us.
In the optimistic scenario, the peak of the wave will reach within a week, and in the pessimistic scenario it will last until the end of September.
Both rely on the fact that the infection rate at this time is 1.13 and that cases, being above 1, continue to increase. A 1.13 means that in a group of 100 carriers of the virus, they will infect 113.
“The increase in this rate since mid-July and especially its values greater than unity indicate that the country is in a new pandemic wave. The size of this new wave will depend on how long the rate remains above the threshold of 1,” the report says.
Assumptions to build expectations
How are these expectations drawn? The analysis begins from the fact that there are three forces that fundamentally determine the transmission of the virus: one positive and two negative.
Positive is the vaccination and the rate taken in recent days, which is faster than in previous months.
The first negative force is the delta variant, more transmissible than the other variants of the virus.
The second negative effect is the easing of measures, either because the authorities are making them more lax or because people are ignoring them.
The advantage is that this single positive force can generate an effect greater than the two negative ones: “Vaccination is a key factor that can more than neutralize the two negative forces,” the document notes.
To build the optimistic scenario, the analysis is based on the following assumptions:
1- Rapid vaccination at a rate of 250,000 doses per week. Our country applied 219,231 doses last week, and the previous 230,383 doses. However, there were weeks with more than 250,000 doses, and the highest vaccination (which coincided with a donation from the US government) was 381,100.
2- Acquired immunity. Vaccine efficacy to be 60% for the first dose and 90% for the second dose; Both are from the third week of application. The efficacy of naturally acquired immunity through infection is 80% in unimmunized people.
3- Variable delta. As of August 13, the proportion of new cases per delta variant is about 40% and that number is increasing at a rate of one percentage point each day.
4- Behavior. The behavior of the population towards infection and health restrictions is no different.
In the pessimistic scenario, one or more of these assumptions are not satisfied.
One of the biggest risks, specifically, relates to point 4. The speed of vaccination can also cause those with an incomplete schedule to raise their personal measurements early.
The analysis warns that “there could be an unexpected adverse side effect of this mass vaccination of young people if many newly vaccinated people feel wrongly protected and abandoned by anti-infective protocols and behaviours”.
The report notes that this is a phenomenon observed in other countries such as Uruguay, “where a paradoxical increase in infections has been accompanied by rapid progress in vaccination for a short period of time.”
This is divided into two parts: one in which the four assumptions are satisfied (also called an “expert”); It is more suitable where one or more assumptions are overcome, i.e. grafted more quickly or delta propagated more slowly.
If the four assumptions are met, the infection rate threshold of 1 will be reached in two weeks, and as of October 13, it will drop to 0.85 (100 infects 85 people).
Cases will continue to increase over the next two to three weeks, peaking at 2,200 daily cases in early September. Then it drops and reaches 1,400 daily cases on October 13.
The number of people hospitalized will peak at 1,000 trainees at the end of August. Within two months, in mid-October, 400 people will be hospitalized with coronavirus, and 200 will be in the intensive care unit (ICU).
In two months there will be about six deaths a day.
In the most favorable scenario, the threshold of 1 will be reached within a week and the infection will begin to decline, and within two months the infection rate will be 0.6 (100 people infect 60).
Cases will peak within a week with just over 1,800 diagnoses per day. By October 15th we will have 200 diagnoses per day.
The country could receive 100 people in hospital within two months, 50 in the intensive care unit.
In two months there will be about two deaths a day.
The projections for this scenario are that the infection rate will remain at similar levels and will decline more slowly to the threshold of 1 near the end of September.
The country will then reach the peak of the new pandemic wave in about a month and a half, with around 3,000 people diagnosed per day.
In terms of hospitalization, a maximum of about 1,200 people will be hospitalized within a month, 500 in the intensive care unit.
There will be approximately 11 daily deaths.
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