The coronavirus pandemic is raging in many countries with its second, third and subsequent waves, and the stringent public health measures have helped contain its spread to some extent.

However, these measures, especially lockdowns and prohibitory orders, have had profound negative impact on the social and economic life. And life is now at risk of becoming more unsustainable and unbearable.

The unprecedented speed and untiring work of researchers and scientists with which vaccines were developed are commendable.

Within less than 12 months after the emergence of the COVID-19 pandemic, several pharmaceutical firms took the challenge and developed vaccines that protect people from the coronavirus.

However, the vaccine rollout is not equitable and slower than expected due to low stocks of jabs at most places, especially in resource-limited countries.

Several vaccines against COVID-19 have already received approval for either full or emergency use in many countries. At present, vaccination is considered to be the last resort in developing herd immunity in most of the people to end the pandemic. In this regard, the World Health Organisation (WHO) deserves kudos for working relentlessly in the field of developing and distributing vaccines in collaboration with partners across the world. The COVAX initiative, established by the WHO in collaboration with GAVI and CEPI, has held out a ray of hope for poor countries.

However, the COVAX initiative has hit a snag. The WHO had planned to inoculate 20 per cent of the population living in 92 poorer countries. But the inability of India to supply Covishield vaccines to the COVAX facility has been a great blow to the WHO.

However, a flicker of hope has emerged on the horizon with the WHO-approved Sinovac vaccine manufactured in China for emergency use.

Like the Covishield vaccine, the Sinovac vaccine is suitable for poor countries as it can be stored at 2-8 degrees Celsius. The vaccine can be administered to people above 18 years of age, with the second dose to be given two to four weeks later.

Antibodies may wane over a period of time. Reinfection is possible once antibodies decline to a level that is no longer protective.

However, it is believed that the infection is likely to be milder. In such a case, a booster dose is needed to remind our immune systems to make more antibodies against the disease.

Developing herd immunity is one of the mechanisms for controlling COV- ID-19. If herd immunity can be developed, all people, including those who are not immune to the disease, can be protected. A certain proportion of the population needs to be infected to spread a disease.

It is called the threshold proportion. If the portion of the people immune to the disease exceeds the threshold proportion, herd immunity can be developed.

It is called the herd immunity threshold.

The percentage of the population that needs to be immune to a disease varies from disease to disease.

Usually, 50-90 per cent of the population needs to develop herd immunity to lower the transmission of a contagious disease. In the case of COVID-19, experts say around 70 percent of the population needs to be immune to it.

Following health safety rules is important to attain herd immunity. Such rules should be followed by even those who have been vaccinated.

If people were to strictly follow the health safety protocols like social distancing, wearing masks and washing hands with soap and water, the infection rate will decline soon.

If people are indifferent to such protocols, the disease will be transmitted thick and fast. What's more, the virus mutates.

Mutated variants of the coronavirus have proved to be more dangerous with more transmissibility, giving rise to the second and third waves of the disease.

Even booster vaccines may be required to cope with mutated strains of the coronavirus.

We cannot afford to let our guard down yet although the daily number of new COVID cases in Nepal has been decreasing for the past several weeks.

It is high time the government conducted a new sero prevalence study to assess the situation, especially since the results of the one conducted in September were not even made publicly available.

The study had found that around 13 percent of the country's population had been infected with the coronavirus until September.

The government must come clear on how and when it is going to conduct another serosurvey to assess the extent of the infection, the risk factors for infection, susceptible groups, and the effectiveness of public health interventions, among other things.

Covishield, Vero Cell and Johnson & Johnson have been used so far in our country for its vaccination programme owing to their cold chain requirements and also approved two additional vaccines, namely, Covaxin and Sputnik-V. It is known that immune responses differ from person to person. Anyone developing a stronger immune response to a vaccine will produce more antibodies as well as memory cells and, therefore, have robust immunity. But it is still not known if a stronger immune response will increase the duration of immunity.

Immunity may also depend on future variants and effectiveness of the vaccines against them.

After all, nobody is safe, until everybody is safe. A large number of the world population needs to be immune to the virus to bring this pandemic to an end.

This can be achieved by either natural immunity following COVID-19 infection or vaccination.

The safest way to develop immunity is with a vaccine.

Vaccines are a wonderful means humanity has often relied on in the past to decrease the death toll due to infectious diseases.

Even as drug makers scramble to adapt their vaccines to deal with the new variants, it is imperative that people continue to follow the COVID-19 safety guidelines.

Dr Budhathoky is central treasurer of Nepal Medical Association

A version of this article appears in the print on August 6 2021, of The Himalayan Times.