In an article published on the website of the Universidade Nova Faculty of Sciences, Manuel Carmo Gomes (epidemiologist) and Carlos Antunes (mathematician) say that the Rt has been above 1.1 and argue that, if it remains as it is, “the number of new cases is expected to double every 30 days”, which could reach 2,000 daily cases in the first half of December.
They recall that, in recent weeks, the ages where the risk of infection has been higher are between 18 and 25 years old, followed by children under 10 years old and young adults between 25 and 40 years old, age groups that increased socialisation after October 1st.
They also recall that there have been occasional outbreaks in nursing homes, stressing that this age group is not the one where cases have increased the most, but it is the one with the greatest risk of developing serious illness, which can lead to hospitalisation and death.
Experts reveal that, since the beginning of October, most new cases of infection have already occurred in fully vaccinated people, stressing that the vaccines remain “highly protective against serious disease”, but that their effectiveness against infection with the Delta variant of virus (the dominant one in Portugal) is less than 80% and decays over time.
“For example, data on the most administered vaccine in Portugal (Comirnaty®, Pfizer) show that in September there were 1.7 infections per 1,000 people who had been vaccinated in July, while for those vaccinated before March there were 3,9/1,000 infections”, they write.
They emphasise that, five to six months after vaccination, the risk of infection increases and, in the elderly or in people with comorbidities, “there have been cases of serious illness with hospitalisation and death”.
Experts insist on the importance of boosting the vaccine and stress that, in the elderly, if it is fast enough, "it should compensate for the decay of protection they had obtained through vaccination at the beginning of the year, allowing them to go through the winter with a low probability of contracting serious disease”.
However, they write that the possibility of vaccinated individuals contracting an infection suggests that "any country will have great difficulty in completely interrupting the circulation of the virus", even with very high vaccine coverage.
"In practice, this means that SARS-CoV-2 will likely persist among us for years to come, and any one of us could have an encounter with the virus and eventually become infected," they add.
Manuel Carmo Gomes and Carlos Antunes also recall that, since the beginning of October, the incidence of the disease has shown a “persistent upward trend” and warn that the persistence of a Rt above 1 “gives an exponential increase in the incidence, which it is likely, in a prolonged situation, to give rise to situations of high hospital pressure”.