Durability of COVID-19 humoral immunity post infection and different SARS-COV-2 vaccines.

BACKGROUND: The global challenge posed by Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) has been a major concern for the healthcare sector in recent years. Healthcare workers have a relatively high risk of encountering COVID-19 patients, making protective immunity against SARS-CoV-2 is a priority for them. This study aims to evaluate the longitudinal measurement of SARS-CoV-2 IgG spike protein antibodies in healthcare workers (HCWs) after COVID-19 infection and after receiving the first and second doses of SARS-CoV-2 vaccines, including Pfizer-BioNTech (BNT162b2) and Oxford-AstraZeneca (AZD1222). METHODS: This longitudinal cohort study involved 311 healthcare workers working in two tertiary hospitals in Saudi Arabia. All participants were followed between July 2020 and July 2022 after completing the study questionnaire. A total of 3 ml of the blood samples were collected at four intervals: before/after vaccination. RESULTS: HCWs post-infection had lower mean SARS-CoV-2 IgG levels three months post-infection than post-vaccination. 92.2% had positive IgG levels two weeks after the first dose and reached 100% after the second dose. Over 98% had positive antibodies nine months after the second dose, regardless of vaccine type. The number of neutralizing antibodies decreased and was around 50% at nine months after the second dose. CONCLUSION: The results show different antibody patterns between infected and vaccinated HCWs. A high proportion of participants had positive antibodies after vaccination, with high levels persisting nine months after the second dose. Neutralizing antibodies decreased over time, with only about 50% of participants having positive antibodies nine months after the second dose. These results contribute to our understanding of immunity in healthcare workers and highlight the need for the continuous monitoring and possible booster strategies.

Seroprevalence of SARS-CoV-2 among high-risk healthcare workers in a MERS-CoV endemic area.

INTRODUCTION: Healthcare workers (HCWs) in Saudi Arabia are a unique population who have had exposures to the Middle East Respiratory Syndrome coronavirus (MERS-CoV) and Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). It follows that HCWs from this country could have pre-existingMERS-CoV antibodies that may either protect from coronavirus disease 2019 (COVID-19) infection or cause false SARS-CoV-2 seropositive results. In this article, we report the seroprevalence of MERS-CoV and SARS-CoV-2 among high-risk healthcare workers in Riyadh city, Saudi Arabia. METHODS: This is a cross-sectional study enrolling 420 high-risk HCWs who are physically in contact with COVID-19 patients in three tertiary hospitals in Riyadh city. The participants were recruited between the 1st of July to the end of December 2020. A 3 ml of the venous blood samples were collected and tested for the presence of IgG antibodies against the spike proteins of SARS-CoV-2 and MERS-CoV using enzyme-linked immunosorbent assay (ELISA). RESULTS: The overall prevalence of SARS-CoV-2 in high-risk HCWs was 14.8% based on SARS-CoV-2 IgG testing while only 7.4% were positive by Polymerase Chain Reaction (PCR) for viral RNA. Most of the SARS-CoV-2 seropositive HCWs had symptoms and the most frequent symptoms were body aches, fever, cough, loss of smell and taste, and headache. The seroprevalence of MERS-CoV IgG was 1% (4 participants) and only one participant had dual seropositivity against MERS-CoV and SARS-CoV-2. Three MERS-CoV positive samples (75%) turned to be negative after using in-house ELISA and none of the MERS-CoV seropositive samples had detectable neutralization activity. CONCLUSION: Our SARS-CoV-2 seroprevalence results were higher than reported regional seroprevalence studies. This finding was expected and similar to other international findings that targeted high-risk HCWs. Our results provide evidence that the SARS-CoV-2- seropositivity in Saudi Arabia similar to other countries was due to exposure to SARS-CoV-2 rather than MERS-CoV antibody.