Over 50 percent of the country’s population has already been exposed to SARS-CoV-2 that causes Covid-19, according to a preliminary report of a large-scale seroprevalence study carried out by the Ministry of Health and Population.

The nationwide study carried out in 76 of the 77 districts of the country, except for Manang, in July, with technical as well as financial support from the World Health Organisation, has found that the majority of the population in densely populated cities across the country has antibodies for the coronavirus.

“A preliminary report of the study shows that over 50 percent of the country’s population was found to have antibodies against the coronavirus,” an official at the Health Ministry told the Post on condition of anonymity.

Antibodies are found in people who are already infected with the coronavirus or have been vaccinated.

“About 97 percent of the work of the seroprevalence survey has been completed and preliminary findings show a large percentage of the population has Covid-19 antibodies,” Dr Krishna Prasad Paudel, spokesperson for the Health Ministry, told the Post. “Though the final report is yet to be prepared, a significant portion of the population, which could be 50 percent, already has coronavirus antibodies.”

As blood samples were collected randomly for the study, samples of the vaccinated population were also included.

According to the latest data of the Ministry of Health, 4,684,509 people, or 15.61 percent of the country’s total population, have taken the first dose of the Covid-19 vaccine while 3,364,157, or 11.21 percent, have been fully vaccinated.

Serology tests look for either immunoglobulin M (IgM) or immunoglobulin G (IgG), the two antibodies against the coronavirus.

Immunoglobulin M is the first antibody developed by the immune system, and can be detected in the bloodstream within a week or two after infection or after a few weeks of vaccination. Immunoglobulin G, meanwhile, is detected only after two weeks.

Blood samples of over 13,500 people, chosen randomly, were collected and tested at the National Public Health Laboratory for antibodies.

The Central Bureau of Statistics helped in choosing the samples to make the collection more scientific, according to Paudel, who is also the director of Epidemiology and Disease Control Division.

Public health experts, however, cautioned that this does not mean that herd immunity, a situation when a large portion of the population becomes immune to a disease, is close to being achieved and that there still is a need to continue with safety precautions.

They say even if the seroprevalence study shows that the majority of the population has natural immunity or is already exposed to the virus, antibodies gained from an infection do not last long and this is shown by multiple international studies.

“I think the result of the seroprevalence study should be taken with caution,” Dr Biraj Karmacharya, an epidemiologist, told the Post. “Even if 50 percent of the population has already been exposed to the coronavirus, the remaining 50 percent is still at high risk of contracting the virus. Authorities should therefore focus on protecting those populations.”

Further, as the virus continues to mutate and more dangerous variants are emerging, risk has not lessened and people already exposed to the coronavirus or those inoculated could get infected again, doctors say.

It is not known yet for which coronavirus variant the antibodies have been detected in the samples tested. The Delta variant, first found in India in December last year, has been the most prevalent among Nepalis.

Karmacharya, who also heads the Department of Community Programmes at Dhulikhel Hospital, said all members of his family are currently infected with the virus even though some of them had already been vaccinated.

“Within three days all of my family members got infected. The Delta variant, which has been wreaking havoc throughout the globe, could be responsible,” said Karmacharya. “We should not forget what is happening in the United States of America.”

Despite the fact that more than 50 percent of the total population in the United States has been fully vaccinated, over 70,000 people are getting infected every day of late.

Similarly, a study carried out in New Delhi in February had shown that 56 percent of the population of the Indian capital had antibodies but it became among the worst affected areas when the second wave hit the country in March.

The Health Ministry had carried out a seroprevalence survey in September 2020 also, which showed that one in eight people, or 13 percent of the population, had been exposed to the coronavirus. And in some districts, the figure was as high as 28 percent.

Doctors say that the seroprevalence survey provides data on the prevalence of the coronavirus in communities, and helps authorities prepare strategies—locate hotspots and take necessary measures to contain the spread of the virus.

“The findings of the seroprevalence study should help authorities prioritise population groups for inoculation and take measures in the areas which have been less exposed to the virus,” Dr Prabhat Adhikari, infectious disease and critical care expert, told the Post.

Hospitals have reported a surge in admissions of serious Covid-19 patients and oxygen manufactures have said that the demand for the life-saving gas has doubled over the past week as a semblance of normalcy has returned although some restrictions are still in place in infection hotspots like Kathmandu Valley.

On Sunday, the Health Ministry reported that 1,793 people tested positive for the coronavirus in 8,088 polymerase chain reaction tests and an additional 419 tested positive in 4,018 antigen tests. The number of active cases stands at 39,298.

With 33 deaths reported on Sunday, the Covid-19 toll has reached 10,292 since the pandemic began in January last year.

Public health experts say that seroprevalence studies should be carried out on a regular basis, as they provide insights into the extent of the infection in the population and help plan the fight against the pandemic accordingly.

Authorities concerned can take a call on where to enforce restrictive measures and increase the availability of infrastructure such as hospital beds, intensive care unit beds, ventilators, isolation wards, and oxygen supply, according to them.

“Whatever the findings of the study, risks of infection are increasing and preventive measures are still relevant,” Dr Sher Bahadur Pun, chief of the Clinical Research Unit at Sukraraj Tropical and Infectious Disease Hospital, told the Post. “If the number of new cases keeps growing at the current pace, health facilities will be overwhelmed soon and we have not forgotten what we saw during the peak of the second wave.”