[ad_1]
But that would not be good, considering that we need such a 10% to 15% immunity of the population?
Another calculation that also comes out of these models is that the smaller these micro buds are, the fewer people are infected to have group immunity. If we hadn’t controlled this at all, we were going to have a major epidemic that lasted about two months and we were left with group immunity. To generate this group immunity in this way, many people were going to become infected. If we are going to generate the same group immunity, not in a single wave, but with two waves, the total of infected in these two waves is less than the total of infected in a giant wave. The shorter these waves are, one after the other, the smaller the number of infected people that allows us to achieve group immunity. It takes longer, but also the total number of people who got sick and the total number of people who die is less.
When you say it takes longer, how long can you predict?
Yes. I have not done it yet, this is going so fast that I have no hands to measure [risos], but it is something that is in my plans.
Taking into account this group immunity rate, from 10% to 15%, what changes in the scenario in Portugal?
Maybe we will have group immunity before the vaccine arrives. I think I don’t know, maybe by the end of the year, I think we can be closer. To say numbers with great certainty I still need to do more studies. This is a subject that we are still studying. I trust the measures of heterogeneity that we have obtained for other diseases and I believe that for this virus they will be similar. Now we will have to take the microdata that is already available in the General Directorate of Health (DGS) and try to measure how much heterogeneity we have in the population, because this is absolutely critical to obtain a more accurate measurement. I think it is extremely positive that we think that we may not have to live like this until we have a vaccine. I hope that natural immunity occurs faster than the vaccine, but if it arrives even faster than expected, even better, of course. But if we can’t count on the vaccine to stop this, I think we will come through this natural immunization route. And it’s one thing to think about how to get 2% or 3% immunity up to 10%. It is three or four times more than what we have for immunity, but if it were up to 70% …
It would be much more difficult to get there …
It would be years before they got there. I hope that this in psychological and emotional terms is very positive. With or without a vaccine, I think getting rid of this virus is within our grasp. Get rid of the virus as a health problem, not the virus itself. The virus may still be present, but hopefully it will keep us less concerned.
I just asked you when we are going to achieve this 10% to 15% immunity. In a few months? I think it is possible to arrive this year?
I would say there for the winter, which would be great so that this does not mix with flu viruses and whatnot.
Do you think it’s possible?
Yes, I think it is possible. Estimates are still not very accurate, I think we have 2% to 3% immunity until the end of this first wave, but I’m not sure. If the rate of asymptomatic patients turns out to be higher than I assume in my models, then we will be even closer. There are still some degrees that can make this even more optimistic. If the waves that are expected to contain this come with less force, our immunity will be greater and greater. We may be saying that this will take until the end of the year, but it will also ease over time.
And until we reach this immunity rate, how many waves can we have? Two three four? Or will it depend on the measures that are imposed as the number of cases increases?
It depends on how big the waves grow, it depends on the size of each wave and it also depends on how many asymptomatic infections occur with each wave, because we do not have data on that, but with antibody tests we will be able to estimate this. I would say maybe four waves, and they will be attenuated. Each one will come with less force than the previous one, but it is a number that I am throwing based on what I know and that has many gaps. We do not have a quantification of asymptomatic individuals and I have not yet studied the microdata that will give us a good measure of the heterogeneity in the susceptibility of the population and that is specific to this virus. I am relying on other diseases.
In his study, he also has a table of strategies to combat the new coronavirus. Portugal used the suppression strategy …
Yes
Regarding this strategy, you see a small wave and then another wave. In the others (mitigation and no intervention), I see a very sharp wave. Does this have to do with the type of measures that are imposed on the population? If Portugal used this suppression methodology, was it correct?
I think if. I have a blue curve, which says mitigation and has a moderate reduction in social contacts: 40% or something like that. Then I have an orange curve, which is the suppression and which has a more marked reduction in the contacts (75%), so the wave is smaller and then another one comes. In the case of the blue wave, it was large enough to induce group immunity, because it infected many people and in orange we did not achieve group immunity, so we are subject to future waves. I did that second wave without restrictions to show the epidemic potential that we still had. He was not suggesting that such a wave should grow out of control.
Would this second wave occur if nothing were done about the increase in the number of cases?
Exactly what would be inconceivable, that was not going to be done. But, in any case, it gives an idea of how much epidemic potential we still have. Naturally, if the cases go up again, we will contain it again. She will come back and want to go up after a few months and we will contain her again.
So instead of having these two waves, we would have the three or four waves that I talked about …
Exactly, we would have several smaller and smaller waves, less and less force. There is a fundamental difference between these two curves, between mitigation and suppression. In the case of mitigation, R0 never falls below 1, so we were able to induce group immunity.
Because the number of infected people is greater.
That is correct. In the orange curve, R0 is reduced to values less than 1. It stops the induction of group immunity, because when R0 falls below 1 we are no longer having that growth. [de casos]. We are simply going to look at the cases that are practically unavoidable, because they were already infected before R0 reached values less than 1 or chains very close to people who were infected when R0 was still greater than 1. From the moment the R0 goes below 1, falls, and eventually reaches values very close to zero. If R0 is forced to stay below 1, we have so few cases that we will not induce group immunity. Now, any relief in the containment of the contacts that makes the R0 return above 1, we again have growth, because the potential is there, people are not immune.
