While the first group of problems does not have practical social impact, and mainly affects medium term political decisions, like vaccine-supply planning for possible future shots, the second might affect, and actually is affecting, individual behaviors, to such a large extent that they reflect in political decisions.
The broad coverage of a few cases of rare thrombosis, disregarding the fact that thrombosis is any way a frequent complication of COVID-19 infection, fed the utopic hope that, giving for granted that the vaccine reduces the death risk, it should not have side adverse effects. This is plainly impossible, and health public policy cannot be determined by such unrealistic wish. হু and medicine agencies have stressed that the low risk of the rare adverse cases does not justify a decision whose potential social benefit is larger, because vaccination is the only tool that can eradicate the pandemic.
In this context, wealthy countries have taken different decisions. Some, like US, Norway, Denmark or Australia, have decided to suspend or not to use a given vaccine, others, like Italy, Spain and other European countries, have not. Planning to return to the discussion of rare adverse cases below, let us just mention that, as consequence of their appearance, significant cancellations of booked vaccination are occurring. In Madrid, a certain day the no-show has been 66% of the expected people, nothing with respect to what is happening in Bulgaria, a country where vaccinations are at minimal level, despite being the second European country for lethality during the last two weeks. However, the most worrying situation is that of those lower-income countries for which it is only accessible the vaccine provided by COVAX program. Indeed, some of these countries, in different continents, refused to receive and use AstraZeneca. As examples, one can mention Venezuela and Haiti, in Latin America, despite the guarantees of safety of the Pan-American Health Organization (PHO), and Cameroun, in Africa, who withdrew the approval for the use of AstraZeneca.
As a matter of fact, in Europe, where few days ago, 80% of the received doses had been used, this percentage goes down to 65% for AstraZeneca, which represents also no more that 20% of the doses to be received in the next quarter.
This shift on the vaccines used and going to be used by wealthiest countries was not based on scientific evidence but is related to the unpleasant inequality between these countries that, having purchased or signed contracts to purchase, a quantity and variety of vaccines largely above their needs, may easily refrain from using a particular vaccine, and lower-income countries unable to make such a choice, since they depend on COVAX program.
Moreover, the worldwide WHO message about the safety of all vaccines, ignored by rich countries despite its scientific soundness, is susceptible of a racist interpretation, as a message directed in practice to lower-income countries, and this offers opportunities to spread fake news. Ultimately, less vaccinations in these countries do affect rich countries as well, insofar this leads to a longer duration of the pandemic, and to the possibility of the virus developing more mutations, but, astonishingly, this risk is overlooked.
For all of these reasons, it is not surprising that these problems have been object of broad discussions:
Regarding the possibility of reinfection
Even if reinfections are rare, there are several open issues, such as how likely they occur, how soon they can take place, and for how long immunity persists. In a review of about two months ago, it was pointed out that current main interest is on vaccination and mutations. Thus, little research is dedicated to reinfections, a difficulty of which is that it is not so easy to distinguish them from a reactivation of a virus that never left the patient. Among these fee studies, one, on Health workers in England, suggests that past infection could reduce the risk of reinfection by 83% for at least 5 months, another, in Denmark, on a much broader sample (4 million people), found a similar result. The COVID-19 outbreak started in January 2020 and it was recognized as a global pandemic in March 2020. This poses an intrinsic limit of 5-8 months to the results of this type of studies, which certainly is going to be extended in future studies, whereas for what concerns the estimate of the protection it is just a matter of further studies.
Regarding vaccine efficiency
Data for different vaccines are quite different and are often presented in connection with different aspects. In the case of AstraZeneca vaccine, its efficiency would be about 76% against symptomatic infection and 100% against hospitalization. For Pfizer/BioNTech, severe cases are reduced by 92%, and hospitalizations by 87%. A Brazilian study showed that the efficiency of the Chinese vaccine is comparable to AstraZeneca for mild-to-severe cases, but much lower, about 50%, for mild cases. However, results from Turkey and Chile are different. This makes doubtful the suggestion that the so-called Chilean paradox may be explained as due to a low efficiency of the Chinese vaccine. Moreover, the predominant use of this vaccine in different countries has been accompanied by different results. In certain cases, like Brazil, Chile and Turkey, there has been a significant increase of new contagions, whereas in others, like Indonesia, Colombia and Dominican Republic, the opposite occurred. Also, the efficiency for prevention rate for transmission, and the possible resilience of mutated viruses to current vaccines are not clear. The latter is one of the factors (together with the uncertainty about the real availability of the necessary vaccines) that may affect the time to reach herd-immunity through the current vaccination campaign.