Natural immunity protects

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I taught bespoke health care as a fundamental principle for decades.

Does natural and hybrid immunity obviate the need for frequent vaccine boosters against SARS-CoV-2 in the endemic phase?

Stefan Pilz John PA Ioannidis

The coronavirus disease 2019 (COVID-19) pandemic has entered its endemic phase

We observe significantly declining infection fatality rates due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

Now

It is crucial but challenging to define current and future vaccine policy,

in a population with a high immunity against SARS-CoV-2,

conferred by previous infections and/or vaccinations.

Vaccine policy must consider the magnitude of the risks conferred by new infection(s),

with current and evolving SARS-CoV-2 variants,

how these risks vary in different groups of individuals,

how to balance these risks against the apparently small, but existent, risks of harms of vaccination,

and the cost-benefit of different options.

More evidence from randomized controlled trials,

and continuously accumulating national health data is required,

to inform shared decision-making with people who consider vaccination options.

Vaccine policy makers should cautiously weight what vaccination schedules are needed,

and refrain from urging frequent vaccine boosters unless supported by sufficient evidence.

The key issue

Whether and how to consider natural immunity after SARS-CoV-2 infections, and hybrid immunity

It is very likely that the large majority of the global population has been infected with SARS-CoV-2,

at least once by late 2022

(Excluding China)

People who have never been infected have probably become a rarity.

It is well established that previous SARS- CoV-2 infections induce a significant and long-lasting protection against reinfections,

and even more so against severe COVID-19.3-6

Lets check the evidence

Risk of reinfection and disease after SARS-CoV-2 primary infection: Meta-analysis

91 studies, n = 15,034,624

Infections n = 158,478 reinfections

During the first 3 months of Omicron wave,

the reinfection rates reached 3.31%.

Overall rates of severe/lethal COVID-19 were very low,

(2-7 per 10,000),

and were not affected by strain predominance.

Conclusions

A strong natural immunity follows the primary infection and may last for more than one year,

suggesting that the risk and health care needs of recovered subjects might be limited.

Although the reinfection rates considerably increased during the Omicron wave,

the risk of a secondary severe or lethal disease remained very low.

The risk-benefit profile of multiple vaccine doses for this subset of population needs to be carefully evaluated.

Back to Pilz, PA loannidis paper

Compared to vaccination by two doses,

natural immunity was associated with a significantly higher protection against SARS-CoV-2 infections before the emergence of Omicron,

when identical times have elapsed since the last immune conferring event.

Denmark

Little viral spread until late 2021,

and then massive infections with Omicron,

ensued in a population that had been widely vaccinated.

Omicron infection fatality rate (IFR) until mid-March 2022,

6.2 per 100,000 infections,

among apparently healthy people 17-72 years

Compared to previous infection waves in Denmark, there was a very significant decline in IFR

Omicron wave

In populations with substantial prior exposure to SARS-CoV-2,

re-infections, less than a quarter of the hospitalization risk,

and one-tenth the mortality

Vojvodina, Serbia

1% of re-infections required hospitalization

Case fatality for re-infections was 0.15%

Accounting for non- ascertained infections,

this suggests that IFR for re-infections,

may be less than 0.05%, (even in people who have not been vaccinated)