Countries worldwide are racing to vaccinate a significant proportion of their populations against COVID in the coming months. The evidence that vaccination decreases the likelihood of severe disease is promising. What is not so clear is whether the vaccines will eradicate the pandemic. To date there has been very little research into whether the vaccines actually decrease viral load (the amount of virus in the body), produce sustained immune responses or are effective against the rapidly increasing band of mutants.
Of course, the hope is that vaccines will slow the reproduction of the virus by reducing the number of susceptible people, as well as lowering viral loads, and thereby viral shedding (when the virus is released into the environment), even in post-vaccination infections. However, the effect of vaccination on viral loads after vaccination is unknown.
Preliminary studies of viral load after COVID infection show that loads were higher in positive samples collected 12-28 days after vaccination than in samples taken during the first 11 days following vaccination. This leads to a variety of hypotheses, none of which have evidentiary support at this time. What is clear, however, is that this finding conflicts with the current advice that the maximal “effect” of vaccination occurs around 14 days after the end of the vaccination course.
In clinical practice the meaning of “effect” is clear. It relates to the impact on an individual. Vaccines can have a relatively immediate effect on reducing symptoms and perhaps some effect on short-term immune stimulation, and reduction of viral load and transmission. In public health, “effect” can have a broader meaning. The importance of community well-being and socio-economic stability must be taken into account.
To do so it is important to look at the global track record of the newer vaccines over the last half century. Effective vaccines that prevent transmission of other RNA viruses such as HIV, Ebola and Zika, are still a long way off. All these viruses have already been detected in the ejaculate of infected men after recovery (and in the case of Ebola transmissible even after five years disease free).
There are also problems with long-term viral persistence with the HPV vaccine. In one study, 17 percent of women who had been vaccinated had persistent infections with carcinogenic HPV types outside currently available vaccines.
The same can be said for the COVID vaccines, in that there are many hurdles to be overcome to design a vaccine against a highly variable virus that targets and impairs immune systems, integrates into the host genes early in the infection and can hide for long periods in bodily reservoirs such as testes, eyes and the central nervous system.
We already have evidence that COVID remains in faeces and semen long after it is cleared from the nose.
This does not mean that people shouldn’t get vaccinated. Quite the contrary. At a minimum, there is good evidence that all the vaccines reduce the severity of COVID when contracted. Reducing morbidity and the long-term effects of the virus are more than sufficient reasons for vaccination as soon as it is available.Vaccines, however, aren’t a panacea. Instead, maybe the answer to ultimately conquering COVID lies in treatments that reduce viral load to undetectable and therefore untransmissible. We already have an example of such a strategy in HIV with the introduction of non-vaccine prevention measures such as Pre Exposure Prophylaxis (PreP) and Post Exposure Prophylaxis (PEP). These pills have revolutionized HIV prevention and transmission. Let us hope that researchers are as fervently seeking non-vaccines treatments for COVID as they are pursuing the vaccine solution.