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Review
. 2023 Mar 14;11(3):655.
doi: 10.3390/vaccines11030655.

Indirect Dispersion of SARS-CoV-2 Live-Attenuated Vaccine and Its Contribution to Herd Immunity

Ursino Pacheco-García  1 , Jeanet Serafín-López  2
Affiliations
Review

Indirect Dispersion of SARS-CoV-2 Live-Attenuated Vaccine and Its Contribution to Herd Immunity

Ursino Pacheco-García et al. Vaccines (Basel). .

Abstract

It has been 34 months since the beginning of the SARS-CoV-2 coronavirus pandemic, which causes the COVID-19 disease. In several countries, immunization has reached a proportion near what is required to reach herd immunity. Nevertheless, infections and re-infections have been observed even in vaccinated persons. That is because protection conferred by vaccines is not entirely effective against new virus variants. It is unknown how often booster vaccines will be necessary to maintain a good level of protective immunity. Furthermore, many individuals refuse vaccination, and in developing countries, a large proportion of the population has not yet been vaccinated. Some live-attenuated vaccines against SARS-CoV-2 are being developed. Here, we analyze the indirect dispersion of a live-attenuated virus from vaccinated individuals to their contacts and the contribution that this phenomenon could have to reaching Herd Immunity.

Keywords: COVID-19; LAVs; SARS-CoV-2 attenuated virus; herd immunity; indirect dispersion.

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Conflict of interest statement

The author has no financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter discussed in the manuscript.

Figures

Figure 1
Figure 1
Proportions of immune individuals achieved by dispersal of the pathogenic microorganism and non-mandatory immunization with non-proliferative vaccines (A) compared to proportions achieved by non-mandatory application of proliferating LAVs (B). The transmission of the live attenuated virus from LAVs vaccinated persons to close unvaccinated individuals induces in them a protective immune response increasing the proportion of immune individuals favoring HI.
Figure 2
Figure 2
Schematic representation of the HI achieved with the non-proliferative vaccine application (A) compared with the hypothetical HI achieved with LAV application (B). Non-proliferative vaccines induce immunity in individuals who receive them; LAV vaccines induce immunity in individuals who receive them, as well as those contacts in whom the attenuated virus spreads, increasing the % of the immune population. The spread of the pathogenic SARS-CoV-2 in a population with 60–70% immune individuals is still possible (C), but it would be more difficult or would no longer occur in a population with a higher of immune individuals (D).
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Grants and funding

Open access funding for this article was supported by Instituto Nacional de Cardiología Ignacio Chávez.

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