SARS-CoV-2 seroprevalence among patients with cancer in Kerala, India, from December 2020 to June 2021 : Cancer Research, Statistics, and Treatment

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SARS-CoV-2 seroprevalence among patients with cancer in Kerala, India, from December 2020 to June 2021

Murhekar, Manoj; Thangaraj, Jeromie W. V.

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Cancer Research, Statistics, and Treatment: Apr–Jun 2022 - Volume 5 - Issue 2 - p 306-308
doi: 10.4103/crst.crst_124_22
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Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) serosurveys measure the proportion of the population having immunoglobulin G (IgG) antibodies against the virus, which could be the result of natural infection or due to coronavirus disease 2019 (COVID-19) vaccination. Serosurveys, when conducted among the unvaccinated population, precisely estimate the disease burden, and measure the extent of spread of COVID-19 infection, as the facility-based (hospital-based) surveillance is likely to miss mildly symptomatic and subclinical cases. Repeated serosurveys in the same geographical area can be useful to track the progress of the pandemic. During the first two years of the pandemic, many serosurveys were conducted in India. A systematic review based on the 53 serosurveys from India indicated a seroprevalence of 20.1% (95% CI, 16.1-25.3) after the first wave and 69.2% (95% CI, 64.5-73.8) after the second wave.[1] The nationwide serosurvey conducted by the Indian Council of Medical Research (ICMR) among the general population from 70 randomly selected districts across 21 Indian states/union territories indicated that the seroprevalence of IgG antibodies increased from <1% during May–June 2020[2] to approximately 7% at the peak of the first wave of COVID-19 (Aug–Sept 2020).[3] The seroprevalence at the end of the first wave was nearly 24% (Dec 2020–Jan 2021).[4] Post-second wave, about 67% of the population and 61% of the unvaccinated individuals in India had IgG antibodies against SARS-CoV-2.[5]

SARS-CoV-2 infection in immunocompromised individuals such as patients with solid tumors or those with hematolymphoid malignancies, organ transplant recipients, patients on dialysis, and patients receiving immunosuppressive drugs, is more likely to progress to severe illness and death than that in immunocompetent individuals.[67] The antibody response, as well as the effectiveness of the COVID-19 vaccines, was found to be lower in such individuals[8] compared to those in immunocompetent individuals. In view of this, priority was accorded to the immunocompromised individuals during the initial rollout of the COVID-19 vaccines in India. Estimating the seroprevalence of IgG antibodies in such populations is therefore crucial as it can guide the policymakers regarding prioritization for vaccination including the number of doses.

In the current issue of the journal, George and colleagues have reported the results of a serosurvey that they conducted among 100 unvaccinated patients with solid tumors in a tertiary care hospital in Kerala between December 2020 and June 2021. The findings of the study indicated that 11% (95% CI, 4.8–17.1) patients had IgG antibodies against the S1-receptor-binding domain (S1-RBD) of SARS-CoV-2.[9] Most COVID-19 infections were mild or asymptomatic in nature. The authors attributed the low seroprevalence among the patients with cancer to the strict compliance with the non-pharmaceutical interventions like masking, hand sanitization, and social distancing in Kerala.

In this single-center study with a small sample size, the authors included a conveniently selected cohort of patients with solid tumors. The serosurvey was conducted over a seven-month period, covering the post-first wave period (Dec 2020–Jan 2021), the introduction of the COVID-19 vaccines (March 2021 onwards for people aged over 60 years and between the ages of 45 and 59 years with comorbidities) as well as the beginning of the delta wave (April 2021 onwards). Since most patients in the study by George et al.[9] were enrolled during the first three months, the seroprevalence estimate is likely to reflect the post-first wave situation in Kerala. From Dec 2020 to Jan 2021, the seroprevalence among the general population in India, as per the ICMR serosurvey was 24.1%. The seropositivity in the three districts selected from the state of Kerala was 14.3%.[4] As per the second serosurvey conducted by the state of Kerala, the seroprevalence in the general population was 10.7% in February 2021.[10]

Immunocompromised individuals are more susceptible to infections because of tumor cachexia, poor nutritional status, and immunosuppression due to the disease or their treatment. However, the seroprevalence estimate due to SARS-CoV-2 infection among patients with cancer observed in the study by George et al.[9] was similar to that of the general population. This is consistent with the findings from studies conducted in other countries. In Japan, post the first wave of COVID-19, no significant difference in seroprevalence was observed between patients with cancer and health care workers (1.0% vs. 0.7%, respectively).[11] Anti-SARS-CoV-2 antibodies were detected in 3.6% of patients with cancer and 3.2% of the health care workers after the first COVID-19 wave in Austria.[12] Additionally, the seroprevalence was similar in immunocompromised children and the immunocompetent pediatric population in Pennsylvania, USA.[13]

Humoral immune response post-infection and vaccination vary widely depending upon the condition causing immunosuppression and the nature of the treatment.[14] Seroconversion after two messenger RNA (mRNA) vaccine doses in individuals with solid neoplasms was high (80–100%) compared to that in patients with hematological malignancies (<60%). Considering the entire group of immunocompromised persons, organ transplant recipients and individuals with end-stage renal disease had a much lower rate of seroconversion (40%).[8] Studies have indicated that patients with solid tumors, both those who were receiving as well as those who had completed treatment were able to mount a similar humoral response to that of healthy individuals, from vaccination as well as infection.[15] Studies also indicate that the proportion of subjects who seroconvert after two doses of COVID-19 vaccines was similar in both patients with solid tumors and healthy controls.[8] Hence a similar level of seroprevalence observed in the study by George et al. [9] between patients with cancer and the general population is expected. The present seroprevalence among the patients with cancer in Kerala is likely to be much higher than that reported in the study, considering the delta and omicron waves in India and the intensification of the COVID-19 vaccination program. The third serosurvey conducted by the Government of Kerala in August 2021–September 2021 estimated an overall seroprevalence of 82.6% (95% CI, 81.5–83.7).[10]

The effectiveness of two doses of mRNA vaccines as prevention against hospitalization for COVID-19 disease in immunocompromised persons was 77% (95% CI, 74-80).[16] Further, an additional dose administered after the primary series has an additive effect on the immunogenicity leading to higher vaccine effectiveness (88%; 95% CI, 81-93) against hospitalization.[17] The current vaccination program in India also recommends an additional third dose for individuals above 60 years with comorbidities. Hence, the unvaccinated or partially vaccinated immunocompromised individuals as well as those who have not received an additional third dose must be prioritized and encouraged to complete their vaccination schedule to attain protection against severe COVID-19. Additional prospective cohort studies among fully vaccinated immunocompromised patients are needed to document the dynamics of long-term immunogenicity.

REFERENCES

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