Evaluation of antibody response to SARS-CoV-2 variants after 2 doses of mRNA COVID-19 vaccine in a correctional facility

Abstract

The SARS-CoV-2 pandemic has posed a challenge for correctional facilities worldwide. People in such settings are more vulnerable to severe forms of infection and it is impossible to completely isolate inmates from the outside world. This study aimed to assess the antibody-mediated immune response in terms of neutralizing antibodies against Alpha, Beta, Gamma and Omicron (sub-lineage BA.1) variants of concern after two doses of mRNA vaccine in correctional officers and inmates from an Italian correctional facility. Most of the correctional officers (56.5%) and inmates (52.3% and 63.6%) retained their neutralizing activity toward the Alpha and Gamma variants, respectively. By contrast, the most striking reduction in comparison with the ancestral virus was found in the antibody response toward the Beta and Omicron variants, in both correctional officers (91.2% and 93.9%) and inmates (85.1% and 92.8%). In addition, subjects who had undergone primary vaccination and had previously been naturally infected had higher neutralizing antibody titers toward the 4 variants than negative subjects. Overall, our findings indicate that primary mRNA vaccination is able to induce neutralizing antibodies toward the ancestral virus, while titers toward variants may vary, depending on the mutations harboring by the variants. Although the correctional setting is often considered distinct or isolated from the wider society and sanitary system, the health of correctional workers and prisoners is inexorably linked to the public health of the country as a whole and it is of paramount importance to monitor the antibody response in these settings.

Keywords: SARS-CoV-2 variants; correctional facility; correctional officers; inmates; mRNA vaccine; neutralizing antibodies.

Figure 1.

Virus neutralization (VN) titers to SARS-CoV-2 virus after 2 doses of mRNA vaccine in correctional officers and inmates. Panel a: VN titers against Wuhan strain in correctional officers; Panel b: VN titers against Wuhan strain in inmates; Panel c: VN titers against Wuhan and Alpha, Beta, Gamma, and Omicron BA.1 variants in correctional officers; Panel d: VN titers against Wuhan and Alpha, Beta, Gamma, and Omicron BA.1 variants in inmates. Dot plots show individual values. Tukey boxplots show outlier values (dots), medians (middle line), third and first quartiles (boxes), while the whiskers display the minimum and maximum values. Horizontal dashed line represents the Lower Limit of Quantification (LLOQ) of VN assay. Statistically significant differences were analyzed by Friedman and Dunn’s multiple comparisons test (p < .05).

Figure 2.

Virus neutralization (VN) titers to SARS-CoV-2 virus after 2 doses of mRNA vaccine in nucleoprotein (NP) positive and NP negative subjects. Panel a: VN titers against Wuhan strain in NP positive subjects; Panel b: VN titers against Wuhan strain in NP negative subjects; Panel c: VN titers against Wuhan and Alpha, Beta, Gamma, and Omicron BA.1 variants in NP positive subjects; Panel d: VN titers against Wuhan and Alpha, Beta, Gamma, and Omicron BA.1 variants in NP negative subjects. Dot plots show individual values. Tukey boxplots show outlier values (dots), medians (middle line), third and first quartiles (boxes), while the whiskers display the minimum and maximum values. Horizontal dashed line represents the Lower Limit of Quantification (LLOQ) of VN assay. Statistically significant differences were analyzed by Friedman and Dunn’s multiple comparisons test (p < .05).