The Pursuit of Herd Immunity

The Indonesian government, like most people in the world, is expecting herd immunity to SARS-CoV-2 to be immediately acquired through vaccination.

Herd immunity is group immunity. In this group several people are not vaccinated (for various reasons) and they enjoy immunity because the greater part of the rest has been inoculated. So far, herd immunity has been reached against various infectious diseases, due to both natural infection and vaccination. It’s not easy to determine herd immunity.

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In general, if 70 percent of people are infected, herd immunity to Covid-19 is expected to be achieved. The figures are obtained by including several calculation components like neighborhood units (Rt) or the number of people infected in every emergence of Covid-19 cases. the proportion of those infected, the proportion of those immunized, and so forth. Experts can of course be mistaken, the figures needed are sometimes incompatible with their calculation. These figures also vary according to countries. Several things offer the prospect that we can gain the herd immunity desired, but there are certainly other things to the contrary.

Previous positive experience

Herd immunity has been repeatedly witnessed. Streptococcus pneumoniae infection in the US decreased dramatically after most children under five were immunized. The number of unvaccinated elderly people who were hospitalized and died declined by at least 50 percent. Herd immunity also ended the appearance of diphtheria in over 150 countries. Measles once also vanished in the whole American continent.

Herd immunity is not an unproven dream. In the three illnesses above, the major cause of herd immunity was immunization.

In some other countries like India, the situation is a bit different. Research in several regions has shown that the rate of population immunity there exceeded 50-60 percent. The accuracy of the data may be debated, but India is indeed one of the countries hardest hit by Covid-19.

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The good thing behind the mishap is that recovery will bring about immunity although it may not last long. Immunity in the Indian community has been acquired after infection rather than vaccination, in view of the as yet very low Covid-19 vaccine coverage there. The number of Indians whose rates of antibodies are examined is in fact not as high as that in advanced countries like Iceland, for instance, which consistently monitors the antibodies of its population. If India’s data are reliable, optimism should be even greater.

The country with the largest record of cases in the world, the US, also hopes to secure antibodies among its greater number of people. However, the US actually doesn’t depend on the data. It relies more on vaccination, which is clearly effective, beneficial and capable of producing herd immunity. In the first week of March 2021, the US was still the country with the biggest numbers of vaccines used and people already vaccinated in absolute terms.

Almost 90 million doses have been used, mostly being mRNA-based vaccines that are “stronger” than those based on virus vectors, proteins and dead viruses. The US’ target is two million vaccine doses per day.

The second and third countries after the US are China (50 million doses) and Britain (20 million doses). Compared with the numbers of people in the countries concerned, the first, second and third positions are just held by Israel (over 98 per 100 people), United Arab Emirates (65 per 100 people) and Great Britain (35 per 100 people). In Israel herd immunity can evidently be evaluated although it has not yet reached final figures. The success of Israel is studied by all experts. Covid-19 vaccines are indeed effective.

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In the US, the dramatic effect is apparent in nursing homes throughout the country. The total of those getting sick has significantly decreased. This is not the case with the group of young people, who in fact haven’t got their turn yet for vaccination.

Caution needed

Although the number of vaccine doses already injected is nearing 300 million, the total is too small compared with the world population now reaching around eight billion. The vaccine coverage figures are not evenly distributed in all countries either. More than 80 nations haven’t yet started immunization programs. Of the list of underprivileged countries assisted by Covax (Covid-19 Vaccines Global Access), only Ghana has obtained aid.

Without even allocations on a global scale, it will be difficult to expect the desired herd immunity. In principle, nobody can feel safe until everybody is safe. The global vaccine supply capacity is also still too low. Not only the US and Europe, the whole world experiences the same thing.

In Indonesia, vaccine coverage is creeping slowly. The numbers of facilities and officers already briefly trained are actually very large. Sadly, there are some field constraints that cannot yet be fully overcome, including the prompt supply of additional vaccine doses. The team’s target to reach 1.5 million daily is still very high and should be revised right away.

In early March 2021, immunization in the country only covered approximately four million. Indonesia in fact is also experienced in surmounting diseases like polio, but the achievement still leaves some questions, especially its vulnerable continuity. Hopefully the history we go through serves as a valuable lesson for the better control of Covid-19.

The speed of simultaneous vaccination is highly decisive. If the time to protect a lot of people is too long, the group receiving vaccines in the initial phase has the risk of losing immunity. All vaccine experts estimate that the duration of Covid-19 vaccination immunity won’t be too long based on the most rational benchmark that the influenza vaccine has had to be annually injected. Nevertheless, solid data on this matter are being gathered and cannot be established within a short time.

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Apart from speed, vaccine distribution cannot yet go beyond ethnic and racial limits. In the US and Israel, for example, the proportions of minorities are very far behind their majority counterparts. It’s actually obvious that Covid-19 knows no such limits. In various publications it can be noticed that immunity after infection is lost at different times. Medical journal publications indicate the presence of a group whose immunity has lasted for more than eight months.

Data di Indonesia on survivors intending to become donors of convalescence plasma find many of them no longer have high rates of antibodies. In the calculation of herd immunity this can cause confusion. Immunity that has gone needs to be promptly strengthened particularly also through immunization.

Virus mutations

Besides the duration of immunity, the other scarier disrupting factor is the presence of variants or mutants. In South Africa, it is evident that the immunity from first infection is ruined in the face of the mutant there. The variants of South Africa and Brazil are indeed more alarming than Britain’s B117, which has also entered Indonesia.

More effective vaccines especially those based on mRNA and virus vectors are still capable of overcoming such mutants with big enough reduction of their capacity. Pfizer vaccine loses at least 20 percent of protection in facing the South African mutant.

Other vaccines may be helpless. Changing the composition of a vaccine actually takes time. Only mRNA vaccines can be instantly modified and this has been and is being conducted by Moderna and Bio-NTech. The modified vaccines can also be used as boosters with relatively stunning effectiveness.

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Mutations are essentially something natural. All living beings want to preserve the existence of their species. The most dreadful virus in terms of mutation is HIV and therefore no vaccine against the disease has been created to date. Influenza virus mutations are also still more terrifying than those of SARS-CoV-2.

For vaccine experts today it’s truly more apparent that the virus causing Covid-19 is a relatively easy target among all causes of illnesses whose vaccines are being researched. The best method of preventing mutations is to restrict the space for virus movement.

Transmission must be stopped. Attempts made by wearing masks, distancing, avoiding crowds and washing hands can effectively serve as a protective shield, besides immunizing oneself with vaccines. The next question is whether these classic efforts can be properly carried out by the greater part of society.

Hopes

With all the plus and minus points offered, herd immunity is not something easy to gain. This ideal target requires collective endeavor. It’s more than mere vaccine production and supply. As a community, humans have once proven the ability to cooperate and remove smallpox, polio (albeit not yet total) and rinderpest from earth. Better collaboration is badly expected at present. Yet if we later face the fact that herd immunity cannot be optimally achieved, we still have reason for optimism.

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Dominicus Husada

Individual protection induced by vaccines and earned by survivors is a very valuable safeguard. At least we can now protect ourselves and our micro environment, saving parents and all senior citizens near us, protecting children who will be growing and leading long lives ahead.

Under such a situation, herd immunity will be more enjoyed as a bonus. For this reason, let’s not hesitate to have ourselves inoculated.

Dominicus Husada, Pediatrician; Head of Children’s Infectious and Tropical Disease Division, Department of Child Health, School of Medicine, Airlangga University/Dr Soetomo Regional General Hospital, Surabaya.

(This article was translated by Aris Prawira