Pass the covid and immunity: Can I get it again? Skip to contentNewtralAfter passing the covid, can I get it again? How long does immunity last?Next
Having passed the covid in the last wave does not guarantee lasting immunity against future infections. It depends on the variant... and you may not know it.
By Mario ViciosaWe explain it to you |9min reading By Mario ViciosaWe explain it to you |9min readingThe omicron variant has multiplied reinfections with the coronavirus six times. More than 100,000 people in Spain have passed the covid and have been infected again, once the latest version of SARS-CoV-2 broke out, which was imposed around the last week of 2021. Experts point out that in the penultimate week As of January 2022, about 10% of the new cases are from re-infected patients, who have lost their immunity.
Summary in 6 keysRe-infections are the engine of omicron and of the incidents that have skyrocketed in almost all the territories where it has entered. An analysis published in Nature confirms that this variant has turned everything upside down not because it multiplies faster in the upper respiratory tract. But for having multiplied the number of susceptible people. The immunity generated by other variants or by the vaccine, against contagion, disappears before.
However, for reinfection to occur there are two key elements, according to the studies published to date and the vision of the immunologists consulted: the time since the first infection occurred and the variant that was involved. In parallel, the time elapsed since the last dose of the vaccine was given seems relevant to avoid reinfection.
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Christmas with coronavirus did not imply Christmas with omicron
First of all, it can only be known with the variant involved in contagion by starting with a PCR. The symptoms are highly variable between people and the evidence is not yet conclusive to ensure that they are characteristic of omicron or delta. So, without a PCR (of a certain type) or genetic sequencing done in the laboratory (not all samples are sequenced), it is not possible to know the variant.
Although we might think that the sixth wave in Spain (fourth in Mexico, third in Argentina, fifth in the US) is the 'omicron wave', the reality is that it is full of cases with the delta variant. According to the sequencing data of the autonomous communities, towards the middle of December, at the very beginning of the explosion, half of the samples were from delta. During the last week of the year, the delta variant was still present in 18% of the samples, according to data collected by GISAID.
That is, if you got it at Christmas, it's perfectly possible that it was delta. And that is relevant to know your degree of immunity and your chances of reinfection.
▸ Distinguish variantsThe key to the gene that does not shine in PCR, how can I know if I have omicron or delta?Case 1: What immunity do I have if I got delta in the sixth wave?
For the IFL-CSIC immunologist Matilde Cañelles, the natural immunity generated with delta is only optimal to be exposed to delta again. But the point is that delta is doomed to extinction. Right now, whoever was infected with delta or another variant is exposing themselves to omicron.
In this case, time and vaccination status seem relevant. Someone with his two doses who got it last summer is perfectly susceptible. Someone who was infected at Christmas, less. There are no records of people re-infected before three months (although they may exist). There are reactivations – people who test negative but who, when reexposed, test positive again weeks later, because they have not finished eliminating the entire virus.
However, it usually takes a long time to get reinfected. The immunologist links this "resistance" to contagion, to the amount of antibodies generated after infection, which "is highly variable among [healthy] people."
Neutralizing antibodies (IgM and IgG) are a first line of defense against the virus. They prevent infection by blocking the spikes of the coronavirus. They occur after the vaccine or after an infection overcome. But they are specific to each variant. Let's say they have a shape that 'fits' better in the shape of the 'key' (spike or S protein) of the tip of the virus. The delta ones work better before delta.
“Imagine you have passed the delta variant. And you've produced tons of antibodies against delta. These antibodies will protect you from omicron. But when they go down in the blood, they will stop protecting you against omicron sooner than they would stop protecting you against delta. Simply because they bind worse to the protein (S)”.
How long will I have enough delta antibodies to 'work' against omicron? Maybe about three months. But once again, it depends on each person. But as a mere reference, we know that the decrease normally occurs after the third month, after recovering from the infection. “It has been confirmed when the antibodies are seen to drop considerably after three or four months. Which doesn't mean your immunity goes away." The T cells (lymphocytes that alert and kill infected cells) and B cells (makers of new antibodies) remain, with good memory.
Although they may not prevent the infection either, they will make the next one mild or asymptomatic.
Case 2: What immunity do I have if I was infected with omicron in the sixth wave?
A priori, very good, if we also had our vaccine doses up to date before the infection. “We believe that only people with problems mounting a good immune response, some octogenarians, etc. they could be infected twice with the same variant," he says. At least in the same season.
It is unknown if SARS-CoV-2 will end up behaving like a seasonal coronavirus. There are indications that this is the case, although for now it is going in waves, guided by new variants. “It is a coronavirus and we knew that immunity is not very long-lasting, especially looking at whether a person could be infected twice in a year with the same cold coronavirus. It has been confirmed when the antibodies are seen to drop considerably after three or four months. Which doesn't mean your immunity goes away."
Once again, the role of T cells is decisive, beyond antibodies. So surely the protection is durable for most people who have passed omicron in the sixth wave if, in addition, they received their full vaccine.
With previous variants, studies such as the one carried out by experts from the La Jolla and Mount Sinai Schools of Medicine (USA) pointed to a specific period of time of around eight or nine months of protection at least . And data on reinfections after the first wave suggest that only 1% –at the top– of the population was reinfected with symptoms.
However, the greatest threat to omicron-generated immunity will be the appearance of a new variant capable of slipping past the defenses set up by the previous infection. Perhaps a future 'pi' variant. According to University of East Anglia Professor Paul Hunter, “Infection with any other variant is going to boost your immunity. That one will be more effective against the same variant, but it will still be good against the others. Against severe symptoms there is greater cross-immunity than what we are seeing in mild cases." That is, having overcome the covid tends to guarantee that you will no longer go to the hospital in future infections.
Should I get a booster dose if I have passed the covid in the sixth wave?
The Health vaccination strategy in Spain dictated until January 25 that people who have been infected with covid ( does not specify the variant) had to wait at least one month before receiving a new (or first) dose of their vaccine, after infection. The Public Health Commission raised that recommended period to five months, although the summons will voluntarily remain open for anyone who wants to get their booster dose one month after diagnosis and recovery. Is it ideal for everyone? Does recent infection equal a third dose? Here the debate begins.
From the Española de Inmunología, Marcos López Hoyos believes that applying it after infection does not make sense from an immunological point of view. "The third dose could be beneficial, especially if six months have passed since the last dose or infectious episode in the general adult population," they explain from this scientific society, in accordance with their recommendations of December 2021.
However, the immunological status from which Spain emerges from this sixth wave is very varied. There are those who have passed omicron and there are those who have recently passed delta; the majority, with their two doses set 'on time' in 2021. That complicates the calculations, according to Cañelles, who recognizes the difficulty of designing a public health strategy for everyone, not tailored to each individual.
Surely, the benefit of this third dose to avoid reinfection is clearer among those who passed delta in the sixth wave. Much lower among those who suffered from omicron. Always, speaking of the healthy general population, not special risk groups. We always talk about preventing new infections (not serious covid). Prevent infections to prevent infections to third parties.
For López Hoyos, "there are data that suggest that the neutralization capacity of the antibodies against omicron recovers to approximately 60% after a third dose." But, once again, it is something temporary and variable between people.
Professor Adolfo García-Sastre, head of the Institute for Global Health at Mount Sinai Hospital in New York, commented in December that taking the third dose just four weeks after infection is perhaps somewhat premature. He is one of those who see that recently passing the covid is equivalent to a vaccine inoculation. A vaccine that he does consider very useful for those who have had covid a long time ago or have not suffered from it. He hopes that a specific vaccine against omicron or all variants will begin to be administered in a few months. Is it preferable to wait for it to go on the market?
A month after my delta infection is the third dose worth it?
Among immunologists, the benefit of a booster dose seems clearly small for those past omicron, but a month? Is it a suitable time for those Christmas 'delta'? Could they wait any longer? “It is a very complicated decision, both from the administration and at the individual level.” Cañelles believes that at least “it is better to wait two months. But if there is a very high transmission, you may as well be interested in putting on the reinforcement now so that you are generating your antibodies as soon as possible. It depends on your degree of exposure, for example”.
África González, professor of Immunology at the University of Vigo, specifies that “repeated infections or vaccinations that are very close in time can lead to depletion of immune cells. The important thing is to leave rest time between one vaccination and another. This does not imply that we are not going to be prescribed a vaccine annually, as with the flu; this is somewhat plausible. Nor is it true that a fourth dose for risk profiles 'stuns' the immune system.
Cañelles concludes: “What is clear is that the third dose has been very important in preventing hospitalizations among people over 60 years of age. Surely the periodic dose regimen (as with the flu) will be maintained for those over 60 years of age.
The Public Health Commission has also issued guidelines for the vaccination of boys and girls. If they have now passed the disease without vaccinating, they will be given a single dose of the vaccine starting eight weeks after diagnosis of the infection. The same time if they have been infected while vaccinated.
The biggest challenge in making an informed decision is a very clear one: we probably don't know which variant we got infected with last Christmas. And this could be relevant. Although in any of the cases, a previous infection or the vaccine usually guarantees that we will not go to the hospital the next time. Even if we rule out the hypothesis that omicron is milder.
As we already explained in this other CoronaFAQ, omicron has a lot of immune escape. That is, it is very different from other variants for which we are better trained by previous infections or vaccines. In other words, “it's not that the antibodies don't work against the new variant. They do work, but worse. So to speak, more is needed to be able to hit the neutralization of the virus. To 'fit' in the new 'drawing of the key' with which the virus makes its way into cells.