Elderly residents of long-term care facilities receive booster shots against SARS-CoV-2

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Advanced age is a significant risk factor for severe coronavirus disease 2019 (COVID-19) compared to children and young adults with COVID-19. Additionally, older people infected with SARS-CoV-2 are rarely asymptomatic and present with severe symptoms such as respiratory failure and multi-organ dysfunction that can lead to hospitalization and / or death. Therefore, the elderly are given priority to receive COVID-19 vaccines.

To study: Characterization of the humoral immune response to BNT162b2 in elderly residents of long-term care facilities five to seven months after vaccination. Image Credit: Pordee_Aomboon / Shutterstock.com

Seniors living in long-term care (LTCF) facilities experience increased exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), increasing their risk of death from COVID-19. At the start of the pandemic, 30 to 60% of all COVID-19-related deaths in Europe were attributed to residents of long-term care facilities. However, older people with co-morbidities and frailty were under-represented or excluded from early COVID-19 vaccine trials.

The emergence of new worrying (COV) variants of SARS-CoV-2, such as the recent Delta variant, and concerns about diminished immunity have sparked discussion about the need for a third COVID-vaccine booster. 19. However, the effect of old age and frailty on immunity to serious disease after vaccination is not entirely clear.

The impact of old age and multimorbidity on the immune response to vaccination

A recent study published on the Preprint Server medRxiv* investigates whether markers of cellular and humoral immunity differ significantly between adults over 75 years of age and a control group six months after vaccination.

The present study also evaluated the effect of drugs and multimorbidity on the immune response. Researchers examined the immune response to the messenger ribonucleic acid (mRNA) vaccine BNT162b2 against SARS-CoV-2 five to seven months after receiving two doses of the vaccine.

Most elderly residents of LTCHs did not have detectable antibodies to the Delta variant

All study participants were required to have previously completed their two-dose schedule of BNT162b2 at the recommended 21-day interval. The vaccination had to be completed five to seven months before the blood sample.

The first group consisted of residents of the LTCF over the age of 75 with no history of SARS-CoV-2 infection, which was confirmed by anti-nucleocapsid antibody tests (N ). While residents were aged 75 to 101, the control group of healthcare workers (HCWs) was aged 18 to 70. Notably, the third group of 14 LTCFs was included in the study which had experienced a breakthrough infection.

Of the 298 SARS-CoV-2 naive residents, 29 (9.5%) had detectable antibodies to the Delta variant, of which 14 (48.3%) had only a borderline antibody titer of 1: 10. Of the 114 HCW controls, 31.6% had detectable neutralizing antibodies.

In the third group of 14 elderly residents, the mean antibody titer was significantly higher compared to the other two groups. In addition, 12 (85.7%) of these residents had detectable antibodies against the Delta variant.

These data demonstrate that 90.5% of ESLD residents did not have detectable neutralizing antibodies against the dominant variant Delta five to seven months after vaccination. In addition, neutralizing antibody titers were higher in those with a breakthrough infection. These observations suggest that LTC residents and healthcare workers would benefit from a third injection of the vaccine six months after ending the two-dose regimen.

Anti-SARS-CoV-2 peak IgG antibody titers (logarithmic) by group. Logarithmic representation in boxplots, 95% CI and IQR (25% to 75%) of group 1 (residents of ELDs 75 years; orange), group 2 (TS in ELDs, 18 to 70 years; blue), and group 3 (residents of LTCH after breakthrough infection, green). The stars represent outliers.

“A linear decline with age was observed in both the resident and healthcare worker group, but was more marked in the elderly. “

The results are consistent with other studies in the elderly, although studies using pseudoviruses have reported higher neutralization rates. One possible explanation for this could be that this study used an authentic Delta variant isolate, rather than a pseudovirus, for neutralization testing. Clinical isolates have additional mutations outside of the peak region, which impact viral value or their sensitivity to antibodies.

A breakthrough infection dramatically increased both antibody titers and the number of individuals with detectable neutralizing antibodies to the Delta variant among the elderly participants. This demonstrates that the humoral immune response is recoverable.

According to the authors, markers of the participants’ cellular response are currently under study and these data may influence the interpretation of the results.

In addition to age, the immunogenicity and efficacy of 219 vaccines can be influenced and suppressed by several factors, including other medical conditions and body composition with very low or high BMI.

*Important Notice

medRxiv publishes preliminary scientific reports which are not peer reviewed and, therefore, should not be considered conclusive, guide clinical practice / health-related behavior, or treated as established information.

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