Re <<Well, if no one ever actually hears about the harm, was there really any harm ?>>
... depends on one's point of view, not as a science-based and humane creature, but as a political animal.
The wonderful thing about the internet is that there is much to easily mine if one can spare a few seconds that otherwise would have been wasted on MSM stuff.
(1) Am told, re oral vaccine for polio back awhile ago ...
... any possible doubts, whether or not well founded, about the safety of the vaccine cannot be allowed to exist in view of the need to assure that the vaccine will continue to be used to the maximum extent consistent with the nation's public health objectives.
(2) The controversy re the vaccine had to do with the unknown that later became known
(3) ... and ...
According to the World Health Organization, routine immunization with OPV must cease after the eradication of poliovirus because of the danger of outbreaks of circulating vaccine-derived poliovirus and the risk of VAPP.
academic.oup.com
Time for a Worldwide Shift from Oral Polio Vaccine to Inactivated Polio Vaccine
To the Editor—Poliomyelitis (often called polio ) is an acute viral infectious disease caused by poliovirus. Polio was one of the most lethal childhood diseases of the 20th century [1].
Two polio vaccines are commonly used throughout the world for poliomyelitis. The first was developed by Jonas Salk in 1952; the second was an oral vaccine developed by Albert Sabin. These 2 vaccines have eradicated polio from most countries and have reduced the worldwide incidence of polio from 350,000 cases in 1988 to just 1300 cases in 2007 [1, 2].
The Salk vaccine, or inactivated poliovirus vaccine (IPV), is based on 3 virulent reference strains—Mahoney, MEF-1, and Saukett. The Salk vaccine provides immunoglobulin G-mediated immunity in the bloodstream, which prevents infection from progressing to viremia and protects the neurons. The Salk vaccine is 60%–70% effective against poliovirus 1 and is 90% effective against both poliovirus 2 and 3 [1].
Oral polio vaccine (OPV) is a live attenuated vaccine: it is produced by passage of poliovirus through nonhuman cells at a subphysiological temperature, which causes spontaneous mutations in the viral genome. OPV is superior to IPV in ease of administration, and there is no need for sterile syringes, as with IPV. OPV also provides longer immunity than does the Salk vaccine. However, OPV has strict requirements for transport and storage, and this is a big problem in some hot or remote areas [2, 3]. Table 1summarizes the key differences between OPV and IPV.
Table 1
Comparison of Oral Polio Vaccine (OPV) and Inactivated Poliovirus Vaccine (IPV)
A major concern about OPV is its ability to revert to a form that can cause paralysis. Outbreaks of vaccine-associated paralytic poliomyelitis (VAPP) have been reported in many countries of the world [2, 4].
In 2005, it was reported that children in a small village in the United States had contracted vaccine-derived polio. In Nigeria, >70 cases have been reported. In 2006, ~1600 cases of vaccine-induced polio occurred in India, according to the Indian Medical Association Sub-Committee on Immunisation's report on the Polio Eradication Initiative [3]. The point to be noted is that these cases were reported during repeated mass-immunization campaigns in which repeated doses of OPV were administered. In 2008, many cases of polio were reported in all provinces of Pakistan, where OPV is used for repeated mass-immunization campaigns. These vaccine-related cases are big challenge for the scientific community if the polio-eradication goal is to be achieved, and there is a need for prompt action to combat the issue [1–5].
According to the World Health Organization, routine immunization with OPV must cease after the eradication of poliovirus because of the danger of outbreaks of circulating vaccine-derived poliovirus and the risk of VAPP. In the regions of the world in which wild-type poliovirus has been eliminated, moving to an IPV or IPV/OPV sequential schedule will reduce or eliminate the risk of VAPP and outbreaks of circulating vaccine-derived poliovirus, as well as increase the likelihood of countries agreeing to stop administering OPV after eradication is achieved. IPV could also be used with OPV in routine schedules to increase immune responses and to decrease the circulation of wild-type poliovirus in countries in which transmission has not been stopped. IPV alone was very successful in eliminating wild-type poliovirus in many European countries and has been used exclusively in the United States since January 2000.
The above observations suggest that OPV has lost its effectiveness in providing herd immunity. It seems that children are getting polio from OPV, and it also seems that OPV is proving to be ineffective in stopping polio transmission from another source. Therefore, the whole world—and especially developing countries—should shift from OPV to IPV, in my opinion. There is still a need for active research in exploring various vaccine strategies for polio and to combat adverse effects associated with polio vaccination; otherwise, the dream of polio eradication will never come true [2–4].
AcknowledgmentsI acknowledge Ms. Gabriele Fieder (University of Vienna) for her kind support.
Potential conflicts of interest. A.S.: no conflicts. |
