Study: SARS-CoV-2 neutralising antibody activity in a highly vaccinated population: Longitudinal serology studies in Singapore. Image Credit: Kateryna Kon/Shutterstock

Infection rates and immunological responses to SARS-CoV-2 infection among migrant workers

In a recent study published on medRxiv* preprint server, researchers assessed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) neutralizing antibody activity in migrant workers.

Study: SARS-CoV-2 neutralizing antibody activity in a highly vaccinated population: longitudinal serological studies in Singapore. Image Credit: Kateryna Kon/Shutterstock

The waning protection induced by natural infection and vaccines of coronavirus disease 2019 (COVID-19) has raised serious public health policy concerns. In addition, data are still lacking on the duration and potency of immunological responses elicited by vaccines as well as natural infections.

About the study

In the current study, researchers investigated COVID-19 infection rates and SARS-CoV-2 immunological responses among a migrant population over a six-week period.

The study included a test cohort of migrant workers between the ages of 19 and 59 who resided in a dormitory infected with COVID-19. The team obtained blood samples from the participants in May 2020 as well as two and six weeks after the initial collection. The community cohort included community-resident adults aged 21 and older who also provided blood samples in November or December 2020.

The team analyzed the serological samples obtained for the presence of SARS-CoV-2 neutralizing antibodies using a surrogate virus neutralization test (sVNT). Information relating to the presence or incidence of other medical conditions such as diabetes, heart disease and hypertension, as well as data relating to the number, type and dates of COVID-19 vaccines received.

The researchers performed the serological analysis of participants who reported having received two doses of any COVID-19 messenger ribonucleic acid (mRNA) vaccine in May or June 2021. The study cohort also included people who had received two and three COVID-19 vaccines. doses by January 2022. For people vaccinated with two or three doses, the team compared the neutralizing activity of SARS-CoV-2 depending on the type of vaccine given.

In addition, the team assessed the cumulative distribution of SARS-CoV-2 neutralizing activity as a function of timing as well as number of COVID-19 vaccine doses received by various populations taking into account factors such as age, sex and pre-existing comorbidities . Decay rates of neutralizing activity were also assessed for people who received two and three doses of mRNA vaccine. The team also compared neutralizing antibody activity among vaccinees in the community cohort and those with mild or asymptomatic COVID-19 infection.


A total of 799 people vaccinated, including 553 Comirnaty, 131 Spikevax and 115 mixed doses of Spikevax and Comirnaty vaccinated. The team noted that the second dose of vaccine was received after a median of 27 days until follow-up in May or June 2021 and 157 days during follow-up in January 2022. Study results showed that people who received the Spikevax vaccine had remarkably higher levels of neutralizing antibody activity after both doses. However, among three-dose recipients, high levels of neutralizing antibodies were found for all vaccines tested with single-dose and mixed-dose vaccinees showing comparable neutralizing activity.

When the team made comparisons based on cumulative distributions, people aged 70 and older had lower knockout activity after receiving two doses through May or June 2021. However, in January 2022, all age groups showed lower and comparable neutralization levels. antibody. This indicated that although the young participants had high levels of neutralizing antibodies initially after vaccination, levels of protection declined to similar levels over time. Notably, neutralizing activity was significantly higher in three-dose recipients compared to two-dose recipients.

The team noted higher neutralizing antibody responses after two doses in females in May or June 2021, which were eventually reduced to levels comparable to male counterparts in January 2022. Administration of one dose Booster vaccine increased neutralizing antibody responses to significantly higher levels with insignificant levels. differences between the two sexes. Additionally, people with hypertension and diabetes had lower neutralizing antibody responses after two doses in May or June 2021 compared to people with no comorbidities.

The team also observed that men aged 60 and over who belonged to the general population group and had received two or three doses of the vaccine in the previous 12 weeks had higher neutralizing antibody responses compared to those of people infected with mild or asymptomatic COVID-19. men from the migrant cohort. Additionally, the team noted that 84% of unvaccinated people had neutralizing antibodies to SARS-CoV-2, indicating a substantial impact of natural infection over the previous six to seven months.


Overall, the study results showed that booster doses of COVID-19 had a potent effect in providing sufficient protection against SARS-CoV-2 infection. Researchers believe that the increase in cases of breakthrough infection necessitates the development of a COVID-19 vaccine specific to SARS-CoV-2 variants.

*Important Notice

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

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