Infection rate and immunological response to SARS-CoV-2 infection in migrant workers

Posted in a recent study medrxiv* Preprint Server, researchers assessed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) neutralizing antibody activity among migrant workers.

Study: SARS-CoV-2 neutralizing antibody activity in a highly vaccinated population: longitudinal serology study in Singapore.  Image credit: Katerina Kohn / Shutterstock
Study: SARS-CoV-2 neutralizing antibody activity in a highly vaccinated population: longitudinal serology study in Singapore. Image credit: Katerina Kohn / Shutterstock

Coronavirus disease 2019 (COVID-19) Natural infection and vaccine-induced protection have raised serious concerns about public health policies. Furthermore, there is still a lack of data concerning the duration and potency of immunological responses elicited by vaccines as well as natural infections.

about study

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

The study included a test group of migrant workers aged 19 to 59 who were residents of a COVID-19-infected hostel. The team obtained blood samples from participants in May 2020 as well as two and six weeks after the initial sampling. The community group consisted of adults living in the community aged 21 years and above who also provided blood samples in November or December 2020.

The team analyzed the obtained serological samples for the presence of SARS-CoV-2 neutralizing antibodies by employing a surrogate virus neutralization test (sVNT). Information related to the presence or occurrence of other medical issues such as diabetes, heart disease and high blood pressure, along with data related to the number, type and dates of COVID-19 vaccines received.

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

In addition, the team assessed the cumulative distribution of SARS-CoV-2 neutralizing activity by time point as well as the number of COVID-19 vaccine doses received by different populations, taking into account factors such as age, gender and pre-existing comorbidities. Evaluated with this in mind. , The inactivating activity decay rate was also evaluated for individuals who received two and three mRNA vaccine doses. The team compared neutralizing antibody activity between vaccines belonging to the community cohort and those experiencing mild or asymptomatic COVID-19 infection.


A total of 799 individual vaccine recipients, including 553 comiRNAs, 131 SpikeVax, and 115 mixed-dose SpikeVax and Comirnati vaccines. The team noted that the second vaccine dose was received after a median duration of 27 days until follow-up in May or June 2021, and 157 days at the January 2022 follow-up. Study results showed that individuals who received the SpikeVax vaccine had higher levels of neutralizing antibody activity after two doses. However, among three-dose recipients, higher neutralizing antibody levels were found for all vaccines analyzed with single- and mixed-dose vaccines, which displayed comparable neutralizing activity.

When the team compared on a cumulative distribution basis, individuals aged 70 years and older had less neutralizing activity after receiving the two doses by May or June 2021. However, as of January 2022, all age groups displayed low and comparable levels of neutrality. Antibodies. This indicated that even though younger participants initially exhibited higher neutralizing antibody levels after vaccination, protection levels decreased to similar levels over time. Notably, neutralizing activity was significantly higher in three-dose recipients than in two-dose recipients.

The team noted higher neutralizing antibody responses after two doses among females in May or June 2021, which eventually decreased to levels comparable to male counterparts in January 2022. Administration of a booster vaccine dose increased neutralizing antibody responses to a significantly higher level with insignificant. difference between the two sexes. In addition, individuals with hypertension and diabetes had no fewer comorbidities than individuals with reduced antibody responses after two doses in May or June 2021.

The team also observed that men aged 60 years and older who belonged to the general population group and who had received two or three doses of the vaccine within the past 12 weeks, had higher rates of infection than mild or asymptomatic COVID-19-infected. Neutralizing antibody responses appeared. Men of the migrant group. In addition, the team noted that 84% of non-vaccinated individuals had anti-SARS-CoV-2 neutralizing antibodies, indicating a substantial impact of natural infection over the past six to seven months.


Overall, the study findings showed that the COVID-19 booster dose had a potent effect in providing adequate protection against SARS-CoV-2 infection. Researchers believe that the rise in cases of breakthrough infection requires the development of a COVID-19 vaccine specific to the SARS-CoV-2 variant.

*Important Information

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


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