A recent study posted to the medRxiv* preprint server assessed the persistence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody five and 12 months post-infection in non-vaccinated patients.
Globally, coronavirus disease 2019 (COVID-19) has caused over 430 million confirmed cases of infection, including 5.9 million deaths to date. Understanding humoral and cellular immunity against COVID-19 is essential to combat the ongoing pandemic. However, there is insufficient data about the persistence of SARS-CoV-2 antibodies in the long term and their role in preventing severe COVID-19 infections.
About the study
The present study examined the total antibody levels produced against SARS-CoV-2 spike glycoprotein up to five and 12 months after diagnosis of infection in non-vaccinated patients.
The study involved residents of South-Eastern Norway of ages 18 years or older who were selected from hospitals, test centers, and laboratories in that region in the period between 28 February 2020 and 17 December 2020. Participants with a COVID-19-positive polymerase chain reaction (PCR) (PCR+) result were matched with two participants with negative PCR results to facilitate the assessment of risk factors, responses to vaccines, and reinfections.
Antibody samples were collected from all participants, and self-reporting questionnaires were answered by each individual three to five months post-PCR diagnosis. The survey had questions regarding the participant’s demographic data, education, income, smoking habits, COVID-19-related hospitalization, presence of comorbidities like asthma, chronic obstructive pulmonary disease (COPD), cancer, and diabetes, and symptoms including fever, cough, sore throat, runny nose, and impaired sense of taste and smell.
Venous blood samples were collected three to five months and 10 to 12 months after the PCR test. Serum samples were developed from whole blood after centrifuging the samples. Total immunoglobulin levels were examined to detect the levels of total antibodies immunoglobulin G (IgG) and IgM in human serum. The interpretation of antibody level changes was assessed by categorizing the antibody levels into four categories, namely, negative (0-0.79), low (0.80-1.99), intermediate (2.00-9.99), and high (more than or equal to 10).
The study results showed that in the study period, 656 PCR+ patients and 923 PCR negative controls were matched according to the time and location of PCR testing. The mean age of the study group was 47.5 years, including 39.8% of males.
While 18% of participants reported asthma, no other comorbidity was prevalent in the study cohort. Notably, symptoms like headache, dyspnea, fever with sweating or chills, nausea or diarrhea, abdominal pain, impaired sense of smell and taste, dizziness, moderate to serious fatigue, and myalgia were reported more often in PCR+ patients than in their PCR-negative counterparts. In contrast, symptoms like sore throat, runny or stuffy nose, and pain upon swallowing were reported more in PCR-negative participants as compared to PCR+ ones. Also, only 6% of PCR+ participants underwent COVID-19-related hospitalization.
Among PCR+ patients, a total of 94% had total antibody levels of 0.8 or above, while 53% showed antibody levels at the upper limit of quantification corresponding to three to five months post-PCR test. Around 212 participants were assessed for antibody levels at both three to five months and 10 to 12 months after PCR test, among which 96% had total antibody levels of 0.8 or above while 53% had antibody levels at the upper limit of quantification for both the periods measured.
A positive correlation was observed between reduced total antibody levels and body mass index (BMI) of 25 kg/m2 and above. Reduced antibody levels were less likely to be found in older participants and patients reporting initial symptoms of sweating and fever with chills.
The study findings showed that total antibody levels against SARS-CoV-2 spike glycoprotein in COVID-19-infected patients persisted in most unvaccinated PCR+ individuals for at least 10 to 12 months after PCR testing was conducted.
The researchers believed that knowledge of antibody responses against SARS-CoV-2 is of prime importance amid the pandemic to facilitate the provision of informed and accurate vaccination strategies.
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.