There are still great unknowns such as how long immunity lasts or if the relaxation of measures can cause an increase in cases in the youngest.
December 27, 2020 was not just any Sunday. Araceli Rosario Hidalgo, born in 1924 and in a nursing home in Guadalajara, received the first vaccine against CoViD-19 administered in Spain. Since then (and until early April) 10 million doses have been administered. Almost 15% of those over 18 years of age (6.8 million) have received at least one, and 6.4% (just over 3 million) the complete guideline.
Although the Government announces a strong acceleration of vaccination, these are still insufficient figures to control the pandemic. The 4th round of National Seroprevalence Study (ENE-COVID), completed in November 2020, showed that 10% of Spaniards (more than 17% in some Community such as Madrid) had antibodies against SARS-CoV-2 due to having had the disease. And we all know how hard it was third wave started the following month.
We are still a long way from herd immunity (if herd immunity is even possible). Let us remember that, at least for the moment, children and adolescents are excluded from vaccination, that less developed countries will take time to be vaccinated (and probably also the poorest groups in developed countries) and that there is the possibility of maintaining animal reservoirs of the virus.
But although vaccination coverage is currently insufficient, 3 million people with the complete program is a lot of people. very many. And they are more every day. What they can and cannot do is an important question. For themselves, for their families, their colleagues and friends and, also, for the economies of their countries. For all.
What can the vaccinated do?
Although Israel has opened the nightclubs for vaccinated people, and the most advanced countries in vaccination herald the return of good times, there is still a lot of uncertainty to clearly define what the vaccinated could or could not do.
The Center for Disease Control and Prevention (CDC) of the United States are perhaps the ones who have made recommendations more specific (and optimistic) for fully vaccinated people (two weeks after receiving the second dose or the first in the case of single-dose vaccines).
For the CDC, and starting this month, The vaccinated should continue to wear a mask and keep their distance in public, with people from more than two households, or with vulnerable people. They should also avoid stuffy spaces and large gatherings, wear a mask on public transportation (and stations), get tested when returning to the US, and get tested (and self-isolate) if they develop symptoms. In addition to following the specific recommendations that may exist in some centers or workplaces.
However, the CDC maintains that fully vaccinated can meet indoors with other fully vaccinated people without a mask or distance, or with unvaccinated people from another household (as long as they are not at risk).
They could also travel without restrictions or testing or quarantine within the United States. They do not even require proof (unless the receiving country requires it) to travel to other countries. Although yes to return to the United States: a test at origin and a new test after 3-5 days, but not quarantine.
They also do not require isolation or the realization of tests to those vaccinated with contact with COVID-19 patients (unless they develop symptoms or reside in a collective center).
Undoubtedly They are big changes. And, to a certain extent, daring. That is why many countries observe with interest the results of these de-escalation strategies in vaccinated people in societies that are not yet fully vaccinated.
Why is relaxation a concern?
We know, from the authorization clinical trials of the different vaccines, that vaccination is extraordinarily effective in reducing cases of covid-19 symptomatic in all age groups. Even when infected the risk of developing severe covid is much lower.
We also know from observational studies with real-world data in U.S, United Kingdom e Israel, that real vaccination retains effectiveness against asymptomatic covid. And, also, even preliminarily, that vaccinated who become infected have lower viral loads than the unvaccinated. If a significant proportion of vaccinated people do not get infected and those who do have a lower viral load, the transmission capacity should noticeably decrease.
No we know at the moment how long it lasts –and, in its case, when and how it decays– the protection offered by vaccination (or natural immunity after the infection has passed). At the moment, and considering the humoral and cellular immunity, the protection seems to resist quite well for at least 6 months. Furthermore, the reported cases of reinfection are anecdotal.
We also know that vaccines perform well against most variants of concern, including the British variant (B.1.1.7). But in the laboratory they lose some effectiveness against the South African variant (B.1.351) and other variants with the E484Y mutation. And we ignore the impact of this partial loss of effectiveness in the real world.
But, and perhaps above all, we do not know the capacity of SARS-CoV-2 –in the more or less immediate future– to evade the immune response produced by vaccines (or natural immunity). Every day that transmission persists – and it is still very high in many countries – it has opportunities to mutate and try. And the future is not written.
In this context of uncertainty, excessive relaxation after vaccination could be problematic. It is worrying, in the first place, that the possible “relaxation” of measures in those vaccinated could lead to an increase in infections among them. Still mostly asymptomatic, and despite their lower transmission capacity, they could be transferred to infections in unvaccinated people, mainly younger populations (those who received the vaccination later).
And although young people (and also those who have been vaccinated) maintain a lower risk of developing severe covid, if transmission is very high they could a problem of saturation of health services and deterioration of health.
There is also concern about the potential development of escape variants or a decrease in the immune response that would lead to the appearance of reinfections. And, above all, the joint combination of all the risks is of concern: high rates in young people, new variants and reinfections.
Prudence should not make us reckless
The alternative of maintaining restrictions for the vaccinated also has significant social costs. In social distance, in loneliness, in pandemic fatigue, in delayed recovery and in increasing poverty. Prudence on the one hand should not make us reckless on the other. Decisions will have to be made balancing risks and benefits at all times.
Exists a lot of uncertainty and the recommendations will change as vaccination advances and new scientific evidence on its impact on transmission becomes available.
The reasonable thing is to follow the rules established by the health authorities at all times (not following them could lead to sanctions). Nowadays in Spain the recommendations do not establish differences between vaccinated and unvaccinated. Nor in other countries with the most advanced vaccination campaign, like the UK.
It is also reasonable that these recommendations be updated as soon as possible, with progress in the number of people vaccinated and with new evidence about the impact of vaccination on transmission (including what we learn from countries that have already begun to relax measures). And without fear of backing down if the epidemiological situation advises it.
In this we must also combine impatience in the search for normalcy and recovery with patience to be able to reach them without more sacrifices than those we are forced to make. It will not be easy to find balance. And we will make mistakes. More bugs. By default and by excess. But we have long known that it is not easy to make decisions in these times.
Finally, it should be remembered that there is also a concern (and a lot) relaxation in the immediate weeks after the first dose, when our body has not yet had time to produce antibodies against SARS-CoV-2 and we still have no protection. Here we do know that we must maintain all the same measures as those who are not vaccinated. In this we have not the slightest doubt or uncertainty.
*This article was originally published on The Conversation.
**Salvador Peiró is a researcher, Health Services Research Area, FISABIO PUBLIC HEALTH, Fisabio.