The level of protective immunity mounted by SARS-CoV-2 infection is not currently known. Therefore, the re-infection probability has been found notably considerable. In this study, we reported 3 cases with suspicious for COVID-19 re-infection. The serology tests revealed that specific SARS-CoV-2 IgG presence is not enough to protect the second viral infection according to the findings. The disease presentation could be less or more severe in the re-infected patients. Moreover, the symptoms might be similar or different in each incident.
Recently, there have been few re-infected COVID-19 case reports. The first case was reported from Hong Kong, a 33-year man, who caught COVID-19 firstly in March with mild symptom presentation. After 4 months and a half, he was found PCR positive with high viral load but asymptomatic. Antibody seroconversion was recorded on the second infection. This might be according to the short lived immunity which faints after a while .
The other reported case, a 25-year man from Nevada, the U.S. was confirmed to be infected with the SARS-CoV-2 twice. The interval between two infections was found 48 days. Surprisingly, he developed more serious disease in the second time including myalgia, cough and shortness of breath and he required oxygen support. The data shows that both patients’ samples had genetic discordance which highlights the re-infection possibility.
Another case report from Brazil, was a nurse who caught COVID-19 infection first in May, 2020 with no specific underlying disease but only sporadically headache. Following the recovery and 38 days with no symptoms, late in June, 2020 she faced severe headache, malaise, myalgia, fatigue, and fever feeling which developed with diarrhea and coughing. Her SARS-CoV-2 RT-PCR test was positive on 5th day of the symptoms. Nevertheless, the SARS-CoV-2 antibody detection rapid test (IgG/IgM) was negative. IgG was detected on 19th and 33rd days after the new onset of symptoms .
The other case report was a 20-year-old woman from Israel, diagnosed with Covid-19 in April, 2020. She presented mild symptoms including fever and cough, with no respiratory distress and was confirmed by a positive nasopharyngeal PCR test. She cleared the virus in May. After three months, she became positive in August although she had no symptoms. Viral serology in August revealed positive SARS-Covid-2 IgG antibodies .
In the case report from Ecuador, the genome sequencing was found different in two incidents. The subject firstly presented mild infection in May whereas the re-infection led to a moderate presentation [28, 29]. SARS-CoV-2 re-infection with worse presentation which results in oxygen support requiring and hospitalization raises concerns re-infection .
United States and Ecuadorboth reportedre-infection cases who experienced increased symptom severity during second infection. The infected cases from Belgium, Hong Kong and the Netherlands, did not present more severe symptoms. There have been three possible explanations for the patient’s more serious symptoms including a higher viral load in the re-infection phase than the first infection, a more virulent version of the virus as the cause of the second incident and the developed antibodies which could result in the subsequent worse infection [30, 31].
In the study from Hong Kong, after two genome sequencing on respiratory specimens during two episodes of a COVID-19 infected patients, the results showed that the firstly viral genome and the second one were belonged to different virus clades with a stop codon at position 64 of orf 8 which led to a truncation of 58 amino acids. They concluded that serological and genomic analyses were strong clues for the re-infection instead of persistent viral shedding. The patient from Hong Kong did not develop Covid-19 antibodies in first disease whereas the second presentation led to antibodies detection. The viral genomes of these studies from Hong Kong, Nevadaand Ecuador were sequenced to determine that the two infections as separate events which resulted differently [28, 29, 32, 33]. Coppolla et al, reported a PCR-confirmed COVID-19 patient who experienced viral reactivation with milder symptoms after 43 days interval and negative PCR. This case had dyslipidemia and chronic ischemic heart disease as underlying diseases .
The other SARS-CoV-2 reactivation case was a 55-year-old female suffering from Philadelphia chromosome-positive, CD20-positive B-ALL, asthma, coronary artery disease and diabetes. After two negative PCR tests and discharge, she re-presented the infection with more severe symptoms. Considering the short time frame, reactivation seems more rational than re-infection. This highlights the risks of recently recovered COVID-19 patients who are on the treatment of immunosuppressive therapy and raises critical questions about the reactivation of SARS-CoV-2 . Based on the observation they suggested that recovered patients must be considered as the carriers of the virus and therefore an additional round of follow up and isolation are needed .
There was a reported case from Italy, who recovered from COVID-19 with positive serology. This 69-year-old woman was suffering from type 2 diabetes mellitus and urinary tract neoplasm. She was followed up for one month with six negative PCR tests. Nevertheless, she presented a second IgM seroconversion along with a positive RT‐PCR after exposure to the virus .
More recently, new SARS-CoV-2 variant in Brazil has reported after the two mutated strains of the virus which were discovered in the U.K. and South Africa. The newly reported variant of the virus belongs to the B.1.1.248 strain which contains 12 mutations in the spike protein. Although viruses are naturally supposed to mutate, the SARS-CoV-2 variants are shown to be more transmissible in comparison with the original which started the pandemic. Therefore, this could result in higher numbers of serious infections and probable additional deaths .
Among the investigated cases in our study, sequencing also suggest that two cases, No#1 & No#3, infected in two separated steps according to the viral mutation (Fig. 1). The amino acid change in the spike protein of the virus, D614G, has emerged early during the pandemic as the viruses harboring this mutation are now dominant in many places worldwide . There have been some evidences that the rapid spread of G614 was due to its more infectious potency than D614 and a higher levels of viral RNA has been assessed in the clinical samples from G614 infections[38, 39].
The recent study by usage of pseudovirus showed that 7% of convalescent sera obtained from recovered COVID-19 subjects contained reduced serum neutralizing activity against 614G in comparison with 614D . According to the time of the first infection, the predominant circulating virus in Iran was D614 which initiated from China. After few months the G614 type was also found in Iran from the European countries. Therefore, we can assume that the second virus was different in the second infection occurrence and re-infection was probable occurrence. Moreover, the symptoms were more serious in the second incidence.
The other case, patient No#2, experienced 157 days of interval between the two incidences and was confirmed negative by RT-PCR. This patient was being followed up in every scene of the disease until he fully recovered. Interestingly, the IgG test was detected monthly in the period between to incidences. Although IgG level raised in the second infection and the symptoms appeared again, the virus type was the same in both infections suggesting that re-activation of the infection occurred (Table 2). As Fig. 2 shows, the N sequencing shows a non-sense mutation T:C based on the similarity between the symptoms and low severity in the second infection, reactivation seems more logical in this case. With the experience of two infection episodes by two SARS-CoV-2 positive specimens separated by a period of 157 days and also the resolution of symptoms with negative RT-PCR, reactivation incidence was more probable.
There has recently been an increasing number of COVID-19 patients with the second episode of the infection in Iran. It seems that the patients who experience the second infection, have high Ct and low viral load. The other important issue is that all the investigated cases in this study were IgG positive at the second infection time with no specific underlying disease. Although, the applying serological platforms are different worldwide and the comparison is not rational, the protection potency of IgG is the fundamental matter. The patients from the USA and Ecuador who had more serious symptoms in re-infection phase strongly highlights this issue. In other cases, that experience mild presentation in the second episode, it is not fully understood that present antibodies play a role or not.