Essay: What is Herd Immunity and Global Vaccine Campaigns

This is an essay and cannot be used as medical treatment or related cases.

What is Herd Immunity:

When most of a population is immune to an infectious disease like corona virus (COVID-19), then herd immunity provides indirect protection or population immunity to those who are not immune to the disease. This occurs when about 95% of the population is infected, but few individuals are symptomatic, according to a study in the Journal of Virology. This study compared the incidence of COVID-19 antibodies in people who were acutely ill with COVID-19 and those who were not, and found the same proportion of people.

Antibodies against COVID-19

When COVID-19 was isolated from serum samples taken from people who had been clinically ill, antibody titers to COVID-19 were similar. This was observed in people who were asymptomatic and those who had recovered from the disease. This suggests that people in whom the virus had been detected may have acquired antibodies against COVID-19. This has important implications for disease control because some people will be unaware of having contracted the virus and will remain immune. This can result in a disease outbreak.

Study of how antibodies may help to the herd immunity:

A study published in the Journal of Virology reported the titers of antibodies in the serum samples of people who had been exposed to respiratory coronavirus in a outbreak in Saudi Arabia. Twenty of 25 serum samples collected from people with possible exposure to the respiratory virus had COVID-19 antibodies, and three of these were positive for antibodies to both COVID-19 and a related coronavirus. These titers were similar in the asymptomatic and clinical groups. Thus antibodies may help to explain the population immunity observed in this outbreak.

Study of presence of antibodies:

The same research team also measured serum antibodies to the flavivirus species Fuziwara and Nipah, a related flavivirus closely related to COVID, in a Saudi outbreak of pneumonia, and found similar titers. This suggests that antibodies may be present against several flavivirus subtypes in the Saudi outbreak.

Serum antibodies to Nipah and Fuziwara viruses

The Saudi study also measured serum antibodies to Nipah and Fuziwara viruses. The studies show that Saudi Arabia has successfully acquired population immunity against Nipah and Fuziwara. This was an important finding, because these viruses are closely related to COVID and previous studies have shown no evidence of large-scale vaccination against either virus.

Two competing views:

Some scientists are wondering if large-scale vaccination programs are needed in Saudi Arabia, given the similar gene sequences to COVID and known subtypes of the viruses. However, other scientists question if we have reached the threshold where additional vaccination programs are not only warranted, but likely to be beneficial. The two competing views are presented here:

View 1.

The Saudi outbreak is unique in that it is the first large-scale human infection with a virus that causes a respiratory illness, causing an outbreak with very high mortality. In addition, the virus strain involved was not circulating before, suggesting that this virus did not cause a large-scale vaccination program.

View 2.

If, as is suspected, the virus is antigenically similar to COVID, the possibility of a future vaccine may exist, and the effort in establishing the present vaccine may have been more than offset by the benefit of future immunity.

Vaccine programs for coxsackievirus:

Of course, the issue is whether the resulting vaccine would offer the same immunity against other large-scale viruses like COVID. I think it does. In fact, when I first looked at the issue of possible Saudi vaccine programs for coxsackievirus, I thought that a Saudi vaccination program was unlikely, given the fact that coxsackievirus is antigenically very different from coxsackievirus. It did not occur to me that antibodies from a Saudi outbreak of coxsackievirus might be protective, because coxsackievirus has no known common ancestor. But if it does, then Saudi Arabia's immune system has a natural defense against it. And it is natural in a way that would not occur if there had been a common antigenic ancestor and a current vaccine.

An important vaccine -pneumococcal conjugate vaccines:

For the most part, the Saudi outbreak, the recent West African outbreak, and the coming Asian outbreak will not affect our future vaccination programs. But there is one vaccine that has the potential to become important, and that is the pneumococcal conjugate vaccines. These vaccines are part of a new line of vaccines that are used to prevent bacterial infections. These vaccines would also have the benefit of being protective against coxsackievirus. And if that happens, it would be an event of huge significance for our health.

pneumococcal conjugate vaccine is capable of eradication:

There is a real possibility that the first large-scale vaccination program with a pneumococcal vaccine would occur in the very near future. It is called the "Advantage Pneumococcal conjugate vaccine (Pneumovax)," and it was licensed in February of 2006. This vaccine, although not yet licensed or approved, has the potential to be the largest and most sweeping pneumococcal vaccination program ever created. The intent of this vaccine is to create a program that would be highly successful in protecting against bacterial infections. It would be highly protective (in a sense that means it would confer lifelong protection) and it is capable of eradication.

Future of Vaccination

These types of vaccines could be the future of vaccination, and as such, they are something to keep an eye on. A vaccine that can protect against coxsackievirus is also a very good thing, and one that is very close to being licensed and being used in mass vaccinations.

The world's largest vaccination program against pneumococcal conjugate vaccines is also being planned for the future. This will be managed by the CDC in collaboration with the Canadian and Australian health authorities. There is a vaccine called Prevnar. This is an injectable vaccine and would be used for immunization against pneumococcus. The vaccine was licensed in March of 2005. When approved, it would be very large, with coverage rates of about 90% at the recommended ages.

Prevnar Vaccine developed in Denmark:

There are some vaccines that are not yet licensed or approved, and they may not become available for several years. One is a new type of pneumococcal conjugate vaccine called Prevnar. This is a new vaccine that was developed in Denmark. It is a very promising vaccine, and is designed to create immunity against pneumococcus. This is a vaccine that has the possibility of eradication, but clinical trials are still ongoing. So the outlook for protection is not completely clear yet. The question of eradication is also being raised for another vaccine called Flublok, which is manufactured by Sanofi Pasteur and is an injectable vaccine. There is also a vaccine called Tamiflu, which is a very rapid series vaccine that should give high levels of protection against the flu. It is hoped that it will provide more protection than currently provided by the seasonal flu shot.

Conclusion:

As you can see, there are many vaccines being tested or being considered for mass vaccination programs. This is a good thing, and we should be glad that some of these vaccines are being done.